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.

Ex Input:
The fossils of dinosaurs that lived millions of years ago can be found in  
 (A) the water of oceans. (B) the ice on ponds. (C) the trunks of trees. (D) rocks in the ground.

Ex Output:
D


Ex Input:
Fertilizers can enable farmers to grow the same crop in a field for several years in a row. Farmers who use less fertilizer often rotate their crops by planting the crop one year and legumes, such as beans and clover, the following year. Fertilizer use and crop rotation with legumes both increase the availability of which of the following nutrients in soil?  
 (A) calcium (B) nitrogen (C) oxygen (D) protein

Ex Output:
B


Ex Input:
The increasing use of internal combustion engines could eventually deplete which resource?  
 (A) wind energy (B) petroleum (C) uranium (D) solar energy

Ex Output:

B