Correct Answer: A

Rationale: Elements within the same group share similar electron configurations in their outermost shells, resulting in comparable chemical properties. Helium and Neon both belong to Group 18 (Noble Gases), explaining their similarities. Boron, Carbon, and Oxygen are not in the same group as Helium on the periodic table. Boron is in Group 13, Carbon is in Group 14, and Oxygen is in Group 16, which are different from Helium's Group 18.

Correct Answer: B

Rationale: Silicon is the correct answer. Silicon is widely used in semiconductors for electronic applications because of its unique properties that allow it to be manipulated to conduct or not conduct electricity effectively. Germanium is also used in semiconductors but to a lesser extent compared to silicon. Gallium and arsenic are not as commonly used in semiconductors like computer chips and solar panels, making them incorrect choices for this question.

Correct Answer: A

Rationale: The half-life of a radioactive isotope is the time it takes for half of the initial sample to decay. After one half-life, half of the radioactive atoms have decayed. The decay rate, however, refers to the rate at which radioactive atoms decay, which is not directly related to the half-life. Choice B is incorrect because it does not correctly define the half-life. Choice C is incorrect as it refers to the creation of new isotopes, not the decay process. Choice D is incorrect as it describes the energy released during decay, which is not the same as the concept of half-life.

Correct Answer: B

Rationale: Negative feedback mechanisms in the endocrine system play a vital role in maintaining hormone levels within a specific range. When hormone levels deviate from the set point, negative feedback signals prompt adjustments in hormone production to bring the levels back to the optimal range. This process ensures a delicate balance of hormones in the body, preventing excesses or deficiencies. Choice A is incorrect because continuously increasing hormone production would lead to imbalances. Choice C is incorrect as a constant release of hormones without regulation would disrupt homeostasis. Choice D is incorrect because disrupting communication between glands would hinder proper coordination and regulation of hormone levels, which is essential for the body's overall function.

Correct Answer: A

Rationale: The correct answer is A: Lachrymal gland. The lachrymal gland, also known as the tear gland, is the almond-shaped gland located above each eye, responsible for producing tears. Tears are a complex mixture of water, electrolytes, proteins, and other substances that help lubricate and protect the eyes from dryness and irritation. Choice B, Lacrimal sac, is incorrect as it refers to a structure that collects tears from the eye. Choice C, Lacrimal duct, is incorrect as it is the tube that carries tears from the lacrimal sac to the nasal cavity. Choice D, Lacrimal papilla, is incorrect as it is a small elevation at the inner corner of the eye where tears drain into the puncta.