SWEET proteins primarily function as:
C fits best: Uniporters. Keep the PHLOEM TRANSLOCATION basics straight and Uniporters stands out as the precise answer. Avoid: A) ATP-driven pumps; B) Antiporters; D) Symporters. Light and flowering items often hinge on which photoreceptor or day-length rule is in play.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.