Earthworms are burrowing animals in wet soil, so they don't come to the ground easily. In summer, after heavy rain, they often live in grass, gardens or farmland.

(1) is cylindrical in length, slightly brown and slender, and consists of more than 100 segments. The front part is a little sharp, the back part is a little round, and there is an endless belt at the front end. The front end is about 13 section from the girdle, and the back end is far from the girdle. The ventral surface is light in color, with bristles in the middle of most segments, which plays a fixed supporting role when the earthworm crawls.

(2) Earthworms breathe on wet body walls, and they breathe oxygen in the air. After the heavy rain, the accumulated water pushes out the oxygen in the gaps in the soil, and the oxygen in the soil is reduced, so that the earthworm cannot breathe in the soil. In order to breathe earthworms (3)A, C and D, and to explore the influence of soil dryness and wetness on the life of earthworms, other conditions (the size, quantity and living conditions of earthworms) should be considered. Pay attention to the uniqueness of control variables, which does not meet the meaning of the question. Options B and 1 are too few earthworms, which are prone to contingency and have too big errors. The results are unconvincing and conform to the meaning of the question.

So the answer is:

(1) Wet body wall

(2) Earthworms climb out of the ground to breathe.

(3)B