You are given a science question (easy-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.

Electron transport in mitochondria results in a chemiosmotic gradient of which particle across the mitochondrial membrane?  
 (A) ADP (B) ATP (C) protons (D) neutrons
C

A scientist uses angstrom units to measure the distance between two points. The scientist is most likely measuring the distance between two  
 (A) atoms. (B) cities. (C) continents. (D) stars.
A

Salt concentration, water temperature, plankton, and the whale shark might all be used in a description of an ocean  
 (A) climate. (B) food web. (C) ecosystem. (D) population.

C