Matric potential (Ψm) is significant in:
C fits best: Dry soils and seeds. Keep the WATER POTENTIAL basics straight and Dry soils and seeds stands out as the precise answer. Avoid: A) Well-watered cells; B) Xylem sap; D) Phloem sap. 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.