Advantage to farming of having many frost-free days

Frost-free days is the term given to the length of time from the last frost of spring and the first frost of fall or winter. For farmers, this is also called the growing season. During this season, crops requiring warmer average temperatures to abundantly grow are cultured. Examples are corn and rice. Without the frost, the crops are exposed to sunlight to propagate their growth. The length of the growing season depends on the geography. The farther away the place is from the Earth's equator, the shorter the frost-free days. In places like USA, it lasts an average of 90 days.

The answer is d if you are on edgenuity.