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.

[Q]: A delta can be seen from the air at the mouth of the Mississippi River. This delta was formed by  
 (A) erosion. (B) weathering. (C) conservation of soil. (D) deposition of sediment.
[A]: D


[Q]: Which involves the greatest variety of cell types?  
 (A) a tissue (B) an organ (C) an organ system (D) an organism
[A]: D


[Q]: Which of the following is not passed from parents to children?  
 (A) hair color and freckles (B) a scar on the knee (C) the need to breathe air (D) the ability to roll the tongue
[A]:
B