You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

The weight of an object can change even when the mass stays the same. Which statement correctly identifies a relationship between mass and weight?  
 (A) The weight of an object depends on its mass and its volume. (B) Gravity affects the weight of an object but not its mass. (C) The mass of an object depends on its weight and size. (D) Magnetic fields can affect mass but not weight.
B

Sandbars form in many rivers because of  
 (A) erosion of cliffs. (B) water flowing into a lake. (C) dams being built by beavers. (D) sediment being moved downstream by water.
D

Three baseball players investigate to see who can throw a baseball the farthest. They mark off an area on the playground for their investigation. Which should they keep constant?  
 (A) Height of players (B) Color of the baseballs thrown (C) Order in which the players throw (D) Spot from which players throw

D

