Primary site of cold perception during vernalization is:
That points to C: Shoot apical meristem. Compared with the other options, Shoot apical meristem is the one that correctly describes the VERNALIZATION & FLOWERING concept. The wrong ones are A) Leaves; B) Roots; D) Flowers. 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.