PCMBS inhibits phloem loading by blocking:
That points to B: Apoplastic sucrose transport. Compared with the other options, Apoplastic sucrose transport is the one that correctly describes the PHLOEM TRANSLOCATION concept. The wrong ones are A) Symplastic pathway; C) Photosynthesis; D) Xylem flow. If you’re stuck, eliminate anything that contradicts a basic fact you already know for this topic.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.