Correct Answer: A

Rationale: The correct answer is A: Amygdala. The amygdala is a key brain structure involved in the processing of emotions, including anxiety. Medications for anxiety disorders often target the amygdala to help regulate emotional responses and control anxiety attacks. The amygdala plays a crucial role in the brain's fear circuit and is essential for the appropriate response to stress and threat perception.

Choices B, C, and D are incorrect because the parietal lobe is primarily involved in sensory processing and spatial reasoning, the hypothalamus regulates basic functions like hunger, thirst, and body temperature, and sensory neurons transmit signals from sensory receptors to the central nervous system, none of which are directly related to the regulation of anxiety attacks.

Correct Answer: A

Rationale: The correct answer is A: 'They are small and soluble.' Small and soluble molecules can easily pass through cell membranes and bind to intracellular receptors. Being small allows them to pass through the membrane, while being soluble enables them to dissolve in the aqueous environment inside the cell.
Choice B is incorrect because large molecules typically cannot pass through the cell membrane easily.

Choices C and D are incorrect because insoluble molecules would not dissolve in the aqueous environment inside the cell, hindering their ability to bind to intracellular receptors.

Correct Answer: B

Rationale:
To convert grams to kilograms, divide by 1,000 since there are 1,000 grams in a kilogram.
Therefore, 1,800 grams is equal to 1.8 kilograms (1,800 / 1,000 = 1.8).
Choice A (0.18) is incorrect because it incorrectly shifted the decimal point.
Choice C (18) is incorrect as it represents the direct conversion without dividing by 1,000.
Choice D (180) is incorrect as it is in the hundreds and not the correct conversion to kilograms. The correct answer is B.

Correct Answer: B

Rationale: Ossification, the process where cartilage is replaced by bone, typically occurs during adolescence, around the age of 18. This is when the growth plates in the bones close, and the bones stop growing in length, leading to the replacement of cartilage with bone tissue.
Choice A (5) is incorrect because ossification primarily occurs during adolescence, not early childhood.
Choice C (42) is incorrect as ossification is completed well before this age, usually during the late teens or early twenties.
Choice D (91) is incorrect as ossification is a process that occurs earlier in life, typically during adolescence, and is not a process that occurs in advanced age.

Correct Answer: D

Rationale: Sucrase is the correct enzyme needed to break down sucrose into its component sugars, glucose, and fructose. Lactase is responsible for breaking down lactose, maltase for maltose, and peptidase for proteins; therefore, they are not the enzymes required to digest sucrose specifically. In the context of digesting birthday cake, which contains sucrose, sucrase is the enzyme needed for this particular sugar.