WHYDOYOUTHINK
a.Curd sets faster in summer than in winter.

b.curd sours faster in summer than in winter

(answer in A part and b part)

a. The curd is formed by the division of the bacteria Lactobacillus in it. When small amount of curd is added to warm milk, the bacteria in the curd divides to convert the rest of the milk also into the curd. But curd sets faster in summer because microbial division rate is high in hot climate than in winters. 

b. Because of the same reason that the microbial activity is high in summers, more lactic acid is produced by the bacteria in summers at a great rate, the curd turns sour faster in summers than in winters.