Picture the mushy zone that exists partway through solidification, the region where solid dendrites and leftover liquid coexist together. Alloy B, with its wide freezing range, spends a long time in this state, and its dendrite arms grow long and interlock with each other, leaving only thin, twisted channels for the remaining liquid to flow through toward regions that are still shrinking as they solidify. These narrow channels choke off easily, so liquid metal from the riser struggles to reach deep into the mushy interior, and the shrinkage that cannot be fed collects as scattered microscopic pores spread throughout the casting instead of one clean cavity. Alloy A, with its narrow freezing range, solidifies with a sharp solid-liquid front, so there is little mushy zone to clog up and the riser can feed the shrinkage easily, concentrating it in one place. So Alloy B is the one more prone to micro-shrinkage, making option (B) correct.