Mineral ions are unloaded at sink tissues mainly by:
Correct option is A, Diffusion or active transport. In MINERAL Transport problems like this, the accurate statement is Diffusion or active transport; the others are common mix-ups. Not these: B) Only diffusion; C) Only mass flow; D) Osmosis. Tissue transport questions usually turn on xylem vs phloem, living vs dead cells, or source vs sink.
Ref: Best CSIR NET Plant Physiology books: Master Unit 6 with Taiz & Zeiger and Salisbury & Ross. Crack Part C experimental questions with top textbooks.