The monthly solar terms remain unchanged.

The answer is a. The change of farming time guides farming activities. ?

This question mainly examines students' ability to solve problems by using what they have learned. Respect for materials is the only secret of doing history well. Looking at the whole material, it is not difficult to find that the change of the 24 solar terms is the change of agricultural time, and the 24 solar terms are used to guide agricultural activities. This is a common-sense question, so the answer to this question is: A. The change of agricultural time guides agricultural activities. ?

Twenty-four solar terms table is a supplementary calendar made by China to guide farming in ancient times, and it is the crystallization of long-term experience and wisdom of working people in ancient China. It was formed in the Spring and Autumn Period and the Warring States Period.

Twenty-four solar terms-beginning of spring: February 4th or 5th is the solar term in beginning of spring every year.

Beginning of spring is the first of the 24 solar terms. It means to begin to enter the spring, "yang and thorns, everything is spring." After beginning of spring, everything is full of vitality, and the four seasons begin now.