Correct Answer: A

Rationale: Arteries are blood vessels that carry oxygen-rich blood away from the heart to various parts of the body. Therefore, they are the vessels that transport blood away from the heart. Veins, on the other hand, transport blood back to the heart. Capillaries are tiny blood vessels where the exchange of nutrients and waste products occurs between blood and tissues, not vessels that transport blood to the heart. Venules are small veins that collect blood from capillaries and connect them to larger veins, rather than transport blood to the heart.

Correct Answer: C

Rationale: Neurotransmitters send chemical messages across the gap between one neuron and another through a structure called the synapse. The synapse is a specialized junction where the axon of one neuron meets the dendrite or cell body of another neuron. Neurotransmitters are released from the axon terminal of the presynaptic neuron and travel across the synaptic cleft to bind to receptors on the postsynaptic neuron, transmitting the signal between the two neurons. Choice A, Schwann cell, is incorrect as Schwann cells are responsible for producing myelin sheath around axons in the peripheral nervous system, not for transmitting neurotransmitters between neurons. Choice B, ganglion, is incorrect as ganglia are clusters of nerve cell bodies outside the central nervous system and do not directly participate in the transmission of chemical messages between neurons. Choice D, axon, is incorrect as the axon is a long, slender projection of a neuron that conducts electrical impulses away from the cell body and towards the axon terminals, where neurotransmitters are released into the synapse, but it is not the structure across which neurotransmitters travel to communicate between neurons.

Correct Answer: B

Rationale: Fertilization typically occurs in the fallopian tube, specifically in the ampulla, which is the widest part of the tube. After ovulation, the released egg travels through the fallopian tube where it may encounter sperm for fertilization to take place. The fallopian tube provides the ideal environment for fertilization due to the presence of cilia that help move the egg and sperm towards each other. The uterus is where the fertilized egg will implant and develop into a fetus, not where fertilization occurs. The endometrium is the lining of the uterus that thickens to support a potential pregnancy but is not the site of fertilization. The ovary releases the egg during ovulation but is not where fertilization occurs.

Correct Answer: A

Rationale: Arteries are blood vessels that carry oxygen-rich blood away from the heart to various parts of the body. Therefore, they are the vessels that transport blood away from the heart. Veins, on the other hand, transport blood back to the heart. Capillaries are tiny blood vessels where the exchange of nutrients and waste products occurs between blood and tissues, not vessels that transport blood to the heart. Venules are small veins that collect blood from capillaries and connect them to larger veins, rather than transport blood to the heart.

Correct Answer: C

Rationale: The correct answer is 'C: skin.' The skin is the primary physical barrier the body uses to prevent infection. It acts as a protective shield that prevents harmful microorganisms from entering the body. The outer layer of the skin, known as the epidermis, acts as a tough physical barrier that blocks the entry of pathogens. Additionally, the skin has special immune cells that can help fight off invaders that manage to breach the physical barrier. Choices A, B, and D are incorrect. While mucous membranes, stomach acid, and urine play important roles in the body's defense against pathogens, the primary physical barrier is the skin, which covers the entire body and provides a robust protective barrier.