Correct Answer: C

Rationale: When a ball is thrown horizontally, its horizontal velocity remains constant throughout its motion. The horizontal distance traveled by the ball is determined by the horizontal velocity and the time taken to hit the ground. In this case, the horizontal distance is calculated as distance = velocity time. Since the horizontal velocity is 10 m/s, the horizontal distance traveled by the ball is 10 m/s time. The time taken to hit the ground is determined by the vertical motion, which is independent of the horizontal velocity. Therefore, without knowing the height of the cliff, we can still determine the horizontal distance traveled by the ball. The horizontal distance is solely dependent on the horizontal velocity and the time of flight, which are not influenced by the height of the cliff. Hence, the correct answer is 30 m. Choice A, 10 m, is incorrect as it does not consider the time of flight. Choice B, 20 m, is incorrect as it does not account for the constant horizontal velocity. Choice D, 'Cannot be determined without knowing the height of the cliff,' is incorrect because the horizontal distance can be calculated independently of the height of the cliff.

Correct Answer: C

Rationale: When a ball is thrown horizontally, its horizontal velocity remains constant throughout its motion. The horizontal distance traveled by the ball is determined by the horizontal velocity and the time taken to hit the ground. In this case, the horizontal distance is calculated as distance = velocity time. Since the horizontal velocity is 10 m/s, the horizontal distance traveled by the ball is 10 m/s time. The time taken to hit the ground is determined by the vertical motion, which is independent of the horizontal velocity. Therefore, without knowing the height of the cliff, we can still determine the horizontal distance traveled by the ball. The horizontal distance is solely dependent on the horizontal velocity and the time of flight, which are not influenced by the height of the cliff. Hence, the correct answer is 30 m. Choice A, 10 m, is incorrect as it does not consider the time of flight. Choice B, 20 m, is incorrect as it does not account for the constant horizontal velocity. Choice D, 'Cannot be determined without knowing the height of the cliff,' is incorrect because the horizontal distance can be calculated independently of the height of the cliff.

Correct Answer: C

Rationale: B cells are primarily responsible for antibody production in the adaptive immune system. When activated, B cells differentiate into plasma cells, which are specialized to produce antibodies. Helper T cells play a crucial role in activating B cells, but they do not directly produce antibodies. Cytotoxic T cells are involved in cell-mediated immunity by killing infected cells, while natural killer cells are part of the innate immune system and target virus-infected and cancerous cells. Therefore, the correct answer is C (B cells) as they are directly involved in the production of antibodies, essential for humoral immunity.

Correct Answer: C

Rationale: When an object is lifted higher above the ground, its potential energy increases. This is because the higher the object is lifted, the greater its potential energy due to the increased distance from the ground. The formula for gravitational potential energy is PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height above the reference point. Therefore, as the height (h) increases, the potential energy (PE) also increases, making choice C the correct answer. Choices A, B, and D are incorrect because when an object is lifted higher, it gains potential energy rather than losing it, keeping it the same, or becoming zero. Thus, the correct answer is that the potential energy of an object increases when it is lifted higher above the ground.

Correct Answer: B

Rationale: In meiosis, there are two divisions: meiosis I and meiosis II. During meiosis I, homologous chromosomes separate, resulting in two daughter cells with half the number of chromosomes as the parent cell. In meiosis II, sister chromatids separate, resulting in a total of four daughter cells, each with a haploid set of chromosomes. Therefore, meiosis involves two divisions and produces four daughter cells. Choice A is incorrect because meiosis involves two divisions, not one. Choice C and D are incorrect as meiosis does not go through four or eight divisions, resulting in eight or sixteen daughter cells.