1. Lymph nodes are small, bean-shaped structures found along lymphatic vessels. What is their primary function?

A. To store excess lymph fluid
B. To produce red blood cells
C. To filter lymph and fight infection
D. To transport lymph to the heart

Correct answer: C

Rationale: The correct answer is C. Lymph nodes are crucial components of the immune system. Their primary function is to filter lymph, which is a clear fluid containing white blood cells, and to fight off infections. Lymph nodes contain specialized cells that help trap and destroy pathogens, such as bacteria and viruses, that may be present in the lymph fluid. This process helps to prevent the spread of infections throughout the body and plays a key role in maintaining overall immune function. Therefore, option C, 'To filter lymph and fight infection,' is the most appropriate description of the primary function of lymph nodes.

2. During normal breathing, which muscle is the primary driver of inhalation by contracting and flattening to increase the volume of the thoracic cavity?

A. Diaphragm
B. Intercostal muscles
C. Abdominal muscles
D. Pectoral muscles

Correct answer: A

Rationale: The diaphragm is the primary muscle responsible for inhalation during normal breathing. When the diaphragm contracts and flattens, it increases the volume of the thoracic cavity, creating a negative pressure that allows air to rush into the lungs. The intercostal muscles also play a role in expanding the ribcage to assist with inhalation. However, the diaphragm is the main driver of the breathing process by creating the necessary space for the lungs to expand and fill with air.

3. What type of energy is stored in food?

A. Mechanical energy
B. Kinetic energy
C. Chemical potential energy
D. Thermal energy

Correct answer: c

Rationale: Food stores energy in the form of chemical potential energy, which can be released during metabolic processes.

4. What is the general formula for an alkyl halide?

A. CnH2n
B. CnH2n+2
C. CnH2n-1X
D. CnH2nO

Correct answer: C

Rationale: The general formula for an alkyl halide is $C_nH_{2n-1}X$, where X represents a halogen (e.g., F, Cl, Br, I).

5. Which energy conversion occurs in a solar cell?

A. Electrical energy to light energy
B. Chemical energy to electrical energy
C. Solar energy to thermal energy
D. Solar energy to electrical energy

Correct answer: d

Rationale: Solar cells convert solar energy (sunlight) directly into electrical energy.

6. What is the main function of lysosomes?

A. Breaking down and recycling cellular waste
B. Storing carbohydrates
C. Synthesizing lipids
D. Transcribing DNA into mRNA

Correct answer: A

Rationale: The main function of lysosomes is to break down and recycle cellular waste. Lysosomes contain digestive enzymes that help break down old or damaged organelles, foreign substances, and cellular debris. This process, known as autophagy, helps maintain cellular health and proper functioning. Storing carbohydrates (option B) is not a function of lysosomes; carbohydrates are typically stored in the form of glycogen in the cytoplasm or as starch in plant cells. Synthesizing lipids (option C) is primarily done by the endoplasmic reticulum and not by lysosomes. Transcribing DNA into mRNA (option D) is a function of the nucleus and not the lysosomes. Therefore, the correct answer is A: breaking down and recycling cellular waste.