Why is the direction of phloem transport opposite in early spring and late fall? a. the temperature changes can reverse the flow in late fall b. the direction of sieve plates in the phloem sieve tube elements become opposite at different times c. the availability of water can change the bulk-flow of food in the phloem d. the source and sink are on opposite sides in early spring and late fall

 D. The source and sink are on opposite sides in early spring and late fall

The source and sink are on opposite sides in early spring and late fall is the direction of phloem transport opposite in early spring and late fall.

Explanation:

Whenever there is a spring in the earliest or in the late fall, the roots which are buried deep down will mobilize the organic material towards the source which includes leaves and the buds.

In this way the direction of phloem transport is changed and then reversed.