Day neutral plants are those which:
Go with B — Flower irrespective of photoperiod. Under PHOTOPERIODISM, this is the standard explanation you’d use in class: it names the real driver or definition, while the rest are nearby but wrong. Not these: A) Require equal day and night; C) Require long nights; D) Require short nights. When two options sound similar, choose the one that matches the textbook definition most tightly.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.