What can adjust the temperature and increase precipitation in human activities is

A, reclamation can increase the land area, that is, the influence of land increases and the temperature difference increases, so it does not meet the meaning of the question;

B. Reclaiming land around the lake reduces the area of the lake, the function of regulating climate of the lake is reduced, the evaporation is reduced, and the temperature difference is increased, which does not meet the problem;

C, afforestation increases the area of forest land, the forest can adjust the temperature, and it can also increase the humidity or precipitation through plant transpiration, so it meets the question;

D, deforestation reduces the area of forest land and reduces the function of forest in regulating climate, so it does not meet the meaning of the question;

So choose: C.