Correct Answer: D

Rationale: The correct answer is the sympathetic nervous system. It controls the 'fight or flight' response by preparing the body for stressful situations. The central nervous system (Choice A) consists of the brain and spinal cord but does not directly control the 'fight or flight' response. The peripheral nervous system (Choice B) includes nerves outside the brain and spinal cord, while the autonomic nervous system (Choice C) regulates involuntary bodily functions but is not specific to the 'fight or flight' response.

Correct Answer: C

Rationale: The correct answer is C, Nucleus. The nucleus is responsible for storing genetic information in the form of DNA. The DNA within the nucleus controls the activities of the cell by directing the synthesis of proteins and regulating gene expression. Choices A, Ribosome, B, Mitochondrion, and D, Cytoplasm, do not store genetic information. Ribosomes are involved in protein synthesis, mitochondria produce energy for the cell, and cytoplasm is a gel-like substance that houses organelles and where many cellular activities occur.

Correct Answer: C

Rationale: The correct answer is the large intestine. The large intestine is responsible for absorbing water and forming feces from undigested food. The stomach's main function is to break down food with acid and enzymes. The small intestine is where most of the nutrients are absorbed into the bloodstream. The esophagus is the tube that connects the mouth to the stomach and does not play a role in absorbing water or forming feces.

Correct Answer: C

Rationale: The correct answer is C, the Lymphatic System. The lymphatic system is responsible for draining clear fluid, known as lymph, throughout the body to protect it from infection. The other choices are incorrect because the pulmonary loop specifically refers to circulation between the heart and lungs, the systemic loop refers to circulation between the heart and the rest of the body, and the immune system is responsible for fighting infections and diseases rather than draining clear fluid.

Correct Answer: C

Rationale: The correct answer is IgG. IgG is the only antibody that can cross the placenta, providing passive immunity to the developing fetus. IgA, IgD, and IgM do not cross the placenta. IgA is mainly found in mucosal secretions, IgD is involved in the activation of B cells, and IgM is the first antibody produced in response to an infection, but it does not cross the placental barrier.