ati teas 7 science

Correct Answer: C

Rationale: The correct answer is C: Exceptional stability of the nucleus. Magic numbers are specific numbers of protons or neutrons that result in a more stable nucleus due to the arrangement of nucleons in energy levels. This stability is a result of closed shells, leading to lower energy states and less tendency for decay. Choices A and B are incorrect as magic numbers actually contribute to increased stability, leading to decreased nuclear instability and lower radioactive decay rates. Choice D is incorrect because magic numbers do not lead to increased instability or enhanced decay rates, but rather to exceptional stability.

Correct Answer: A

Rationale: The P wave on an ECG represents atrial depolarization. During the cardiac cycle, the electrical impulse originates in the sinoatrial (SA) node, causing the atria to contract. This depolarization of the atria is reflected as the P wave on the ECG. This occurs before the ventricles depolarize (choice B), repolarize (choice D), or before the atria repolarize (choice C). Therefore, the correct answer is A because the P wave specifically represents atrial depolarization in the cardiac cycle.

Correct Answer: C

Rationale: The correct answer is C: Luteinizing hormone (LH). LH surge triggers ovulation by causing the mature ovarian follicle to release the egg. Estrogen and progesterone play important roles in regulating the menstrual cycle but are not the primary triggers for ovulation. FSH stimulates the growth of ovarian follicles but does not directly trigger ovulation.

Correct Answer: C

Rationale: The correct answer is C: Isotonic solution. An isotonic solution has the same concentration of solute as another solution, leading to no net movement of water across a semipermeable membrane. This term is commonly used in biology and medicine to describe solutions with equal osmotic pressure. Incorrect answers: A: Saturated solution - A saturated solution is one in which the maximum amount of solute has been dissolved at a given temperature. B: Unsaturated solution - An unsaturated solution has a lower concentration of solute compared to what it could dissolve at a given temperature. D: Concentrated solution - A concentrated solution simply means a solution with a high amount of solute dissolved in a solvent, but it does not necessarily mean it has the same concentration as another solution.

Correct Answer: B

Rationale: Platelets are responsible for blood clotting, which is crucial for preventing excessive bleeding when a blood vessel is injured. They adhere to the site of injury and form a plug to stop bleeding. This function is essential for maintaining hemostasis in the body. Platelets do not carry oxygen like red blood cells (Choice A), fight infection like white blood cells (Choice C), or transport nutrients like plasma (Choice D).