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.

Typically, sedimentary rocks are formed  
 (A) only in erupting volcanoes. (B) only under great pressure and high temperatures. (C) below Earth's surface as magma cools and crystallizes. (D) from materials that settle.
D

A cut to the skin is treated with antiseptic first to avoid  
 (A) an immune response. (B) a bacterial infection. (C) bruising of tissues. (D) an allergic reaction.
B

A plover bird eats bits of food that become stuck in a crocodile's teeth without being hurt. The crocodile gets its teeth cleaned and the bird gets food. Which type of relationship exists between the bird and the crocodile?  
 (A) mutualism (B) commensalism (C) parasitism (D) phototropism

A