1. Autoimmune diseases occur when the immune system mistakenly attacks healthy body tissues. What is a potential cause of autoimmune diseases?

A. Deficiency in essential vitamins and minerals
B. Exposure to environmental toxins
C. Breakdown in immune cell self-tolerance mechanisms
D. All of the above

Correct answer: C

Rationale: The correct answer is C. Autoimmune diseases are triggered by a breakdown in immune cell self-tolerance mechanisms, where the immune system fails to recognize 'self' from 'non-self' cells, leading to attacks on healthy tissues. While deficiencies in essential vitamins and minerals or exposure to environmental toxins can impact immune function, the root cause of autoimmune diseases is primarily attributed to the breakdown in self-tolerance mechanisms. This breakdown can be influenced by genetic predisposition, environmental factors, and other triggers, leading to the development of autoimmune conditions.

2. Which of the following is NOT a typical component of healthy semen?

A. Sperm
B. Fructose (sugar)
C. Prostaglandins
D. Urine

Correct answer: D

Rationale: The correct answer is D: Urine. Semen is a mixture of fluids from various glands in the male reproductive system. It typically contains sperm, fructose (sugar) to provide energy for the sperm, and prostaglandins to aid in sperm motility. Urine is not a normal component of healthy semen. It is important to note that urine and semen travel through different pathways in the male body, and they should not mix. Therefore, the presence of urine in semen would indicate a potential issue or infection in the urinary system. Understanding the components of healthy semen is crucial for assessing male reproductive health and fertility.

3. A birdbath has a hemispherical bowl with a diameter of 30cm. What is its volume?

A. 675 cu cm
B. 1350 cu cm
C. 2700 cu cm
D. 4050 cu cm

Correct answer: C

Rationale: Use half the formula for a sphere's volume: (2/3) * Ï€ * (radius)^3. Calculate the radius (15cm) and substitute: (2/3) * Ï€ * (15cm)^3 â‰ˆ 2700 cu cm.

4. What defines the period of a wave?

A. The number of waves passing a point per unit time
B. The distance between two adjacent crests or troughs
C. The time it takes for one complete wave cycle to pass a point
D. The maximum displacement of particles in a medium due to the wave

Correct answer: C

Rationale: The period of a wave is defined as the time it takes for one complete wave cycle to pass a point. It is typically measured in seconds and is inversely related to the frequency of the wave. The period is not related to the number of waves passing a point per unit time (A), the distance between two adjacent crests or troughs (B), or the maximum displacement of particles in a medium due to the wave (D).

5. Which of the following organs is NOT directly involved in the mechanical breakdown of food?

A. Mouth
B. Stomach
C. Small intestine
D. Esophagus

Correct answer: D

Rationale: The correct answer is D, esophagus. The esophagus is a muscular tube that connects the mouth to the stomach, but it is not directly involved in the mechanical breakdown of food. The mouth is responsible for the initial mechanical breakdown of food through chewing, the stomach further breaks down food through muscular contractions, and the small intestine aids in the digestion process. However, the esophagus primarily serves to transport chewed food from the mouth to the stomach via peristaltic movements, without actively breaking down the food itself.

6. The main function of the nephrons is to:

A. Store urine
B. Filter blood and remove waste products
C. Produce hormones
D. Control blood pressure

Correct answer: B

Rationale: The correct answer is B: 'Filter blood and remove waste products.' Nephrons are the functional units of the kidneys responsible for filtering blood to remove waste products, excess ions, and water, while reabsorbing essential substances like glucose and amino acids. This process forms urine, which is stored in the bladder before being excreted. Options A, C, and D are incorrect because nephrons do not store urine, produce hormones, or directly control blood pressure; although the kidneys do play a role in long-term blood pressure regulation through mechanisms like the renin-angiotensin-aldosterone system.