Correct Answer: B

Rationale: The primary function of the cell membrane, also known as the plasma membrane, is to regulate the movement of substances in and out of the cell. It acts as a selectively permeable barrier, allowing specific molecules to pass through while blocking others. This role is crucial for maintaining the internal environment of the cell by enabling essential nutrients to enter and waste products to exit. While the cell membrane provides some structural support for the cell, its main function is substance transport. Protein and lipid synthesis predominantly occur in organelles like the endoplasmic reticulum and Golgi apparatus, and storing genetic material is the nucleus's responsibility. Therefore, choices C (To synthesize proteins and lipids) and D (To store genetic material) are incorrect as these functions are carried out by other cell organelles, not the cell membrane.

Correct Answer: B

Rationale: Deuterium, as an isotope of hydrogen, has an atomic number of 1 and a mass number of 2. The nucleus of deuterium contains one proton (as in all hydrogen atoms) and one neutron, totaling 2 nucleons in the nucleus. Therefore, the correct answer is that deuterium's nucleus contains a proton and a neutron. Choices A, C, and D are incorrect. Deuterium is not just a single proton (A), doesn't have two protons and an electron (C), and doesn't contain two neutrons (D). The correct composition of deuterium's nucleus is one proton and one neutron.

Correct Answer: B

Rationale: Acetylcholine is the neurotransmitter responsible for stimulating muscle contraction at the neuromuscular junction. When an action potential reaches the end of a motor neuron, acetylcholine is released into the synaptic cleft and binds to receptors on the muscle cell membrane, leading to muscle contraction. Dopamine, serotonin, and norepinephrine are neurotransmitters that have different functions in the nervous system and are not directly involved in stimulating muscle contraction. Dopamine is involved in reward and pleasure pathways, serotonin regulates mood and behavior, and norepinephrine is involved in the 'fight or flight' response.

Correct Answer: C

Rationale: The term for the particles moving within a substance is typically 'molecules' or 'atoms,' depending on the state of matter. In this context, 'molecules' represent the particles moving around within a substance, especially in the liquid and gas states, while 'atoms' are the fundamental building blocks of matter. 'Ions' are charged particles that can be present in a substance but are not necessarily the primary particles in motion. 'Kinetic energy' is not a term used to describe the particles themselves but rather the energy associated with their motion.

Correct Answer: C

Rationale: Electromagnetic waves do not require a medium for propagation as they consist of oscillating electric and magnetic fields that can travel through a vacuum. This property allows electromagnetic waves, such as light, radio waves, and X-rays, to propagate through space. In contrast, transverse and longitudinal waves require a medium (solid, liquid, or gas) for propagation. Transverse waves have vibrations perpendicular to the direction of energy transfer, while longitudinal waves have vibrations parallel to the direction of energy transfer. Surface waves, which are a combination of transverse and longitudinal waves, also need a medium for propagation. Understanding the distinction between these wave types is essential in various fields, including physics and communication technologies.