Deficiency symptoms of immobile nutrients appear first in:
B fits best: Young leaves. Keep the PSS- Sec-F-Transport basics straight and Young leaves stands out as the precise answer. Avoid: A) Older leaves; C) Roots; D) All tissues. 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.