FT protein reaches the shoot apex through:
Phloem (C) is correct here. This is core VERNALIZATION & FLOWERING: once you know the definition or pathway step, Phloem is the clear fit. The wrong ones are A) Xylem; B) Diffusion; D) Apoplast. If the topic is about gradients or potentials, water/solutes move from higher to lower of the relevant quantity.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.