Xylem vessels are dead at maturity to:
That points to C: Reduce resistance to water flow. Compared with the other options, Reduce resistance to water flow is the one that correctly describes the WATER TRANSPORT concept. The wrong ones are A) Store nutrients; B) Conduct food; D) Increase metabolism. 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.