31. Which of the following does not appear to involve active transport across membranes?(A) the movement of sugar from mesophyll cells into sieve-tube members in corn(B) the movement of mineral nutrients into cells of the root cortex(C) K+ uptake by guard cells during stomatal opening(D) the movement of mineral nutrients from the apoplast to the symplast(E) the movement of sugar from one sieve-tube member to the next