1. The largest bone in the human body is the:

A. Femur (thigh bone)
B. Tibia (shin bone)
C. Humerus (upper arm bone)
D. Scapula (shoulder blade)

Correct answer: A

Rationale: The correct answer is A: Femur (thigh bone). The femur is the longest and strongest bone in the human body, located in the thigh region. It plays a crucial role in supporting the body's weight and facilitating movement. The tibia (B) is commonly known as the shin bone and is located below the femur. The humerus (C) is the upper arm bone, and the scapula (D) is the shoulder blade. However, neither of these bones is the largest in the human body. Understanding the anatomy of the skeletal system is essential for identifying the largest bone in the body, which is the femur.

2. A lab report shows a potassium level of 4.5 millimoles per liter (mmol/L). Is this within the normal range of 3.5 to 5.3 mmol/L?

A. No, it is too low.
B. Yes, it is within the normal range.
C. No, it is too high.
D. Cannot be determined without additional information.

Correct answer: B

Rationale: The potassium level of 4.5 mmol/L falls within the normal range provided (3.5 to 5.3 mmol/L). 5. An infant's feeding schedule prescribes 120 milliliters of formula every 3 hours. How many ounces of formula should be prepared for a 24-hour period?

3. Vaccines work by stimulating the immune system to develop:

A. A physical barrier against pathogens
B. An inflammatory response
C. Immunological memory to a specific pathogen
D. Phagocytes to engulf pathogens

Correct answer: C

Rationale: The correct answer is C: 'Immunological memory to a specific pathogen.' Vaccines work by introducing a harmless form of a pathogen or a piece of it to stimulate the immune system. This exposure triggers the production of antibodies and memory cells specific to that pathogen. These memory cells 'remember' the pathogen, allowing the immune system to respond more effectively and rapidly if exposed to the actual pathogen in the future. Options A, B, and D are incorrect because vaccines do not create a physical barrier, induce a general inflammatory response, or directly cause phagocytes to engulf pathogens; instead, vaccines enhance the immune system's ability to recognize and combat specific pathogens.

4. Molecular clocks utilize the accumulation of mutations in DNA sequences to estimate the evolutionary divergence time between species. This method relies on the assumption that:

A. The rate of mutation is constant across all genes and all species.
B. Species with more morphological similarities diverged more recently.
C. Mutations are always beneficial and contribute to increased fitness.
D. The fossil record provides the most accurate estimates of evolutionary relationships.

Correct answer: A

Rationale: Rationale: A molecular clock is a method used to estimate the time of divergence between species by measuring the accumulation of mutations in DNA sequences. This method relies on the assumption that mutations occur at a relatively constant rate over time. If the rate of mutation were not constant, it would be challenging to accurately estimate the evolutionary divergence time between species. Therefore, option A is the most appropriate choice as it aligns with the fundamental principle underlying the molecular clock hypothesis. Option B is incorrect because the assumption that species with more morphological similarities diverged more recently does not directly relate to the concept of molecular clocks and the accumulation of mutations in DNA sequences. Option C is incorrect because mutations are not always beneficial and do not always contribute to increased fitness. Mutations can be neutral or deleterious as well, and their accumulation is what is used to estimate evolutionary di

5. A new material is claimed to be stronger than steel. You design an experiment to test this claim. What is the MOST important control variable?

A. The size of the material samples.
B. The temperature at which the test is conducted.
C. The force applied to the material.
D. The color of the material.

Correct answer: A

Rationale: The size of the material samples is the most important control variable because it ensures that the comparison between the new material and steel is fair and accurate. By keeping the size consistent, any differences in strength can be attributed to the material composition rather than variations in sample size. Controlling for size helps eliminate confounding variables and increases the reliability of the experiment results. Temperature, force applied, and color are not as critical for directly testing the strength comparison between the new material and steel.

6. What is the scientific term for scar tissue?

A. Epithelial tissue
B. Fibrous connective tissue
C. Cartilage
D. Adipose tissue

Correct answer: B

Rationale: The correct answer is B: Fibrous connective tissue. Scar tissue is formed during the process of wound healing, where fibroblasts produce collagen fibers to repair damaged tissue. This results in the formation of fibrous connective tissue, which is different from epithelial tissue (A), cartilage (C), and adipose tissue (D). While epithelial tissue lines surfaces and organs, cartilage is a type of connective tissue found in joints, and adipose tissue is a type of connective tissue that stores energy in the form of fat. Scar tissue, on the other hand, is primarily composed of collagen fibers and is classified as fibrous connective tissue.