The correct option is B Malvaceae
When all the filaments of stamen fuses to form a single bundle is called as monoadelphous. It is a key character of the androecium of the Malvaceae. It has pentamerous, actinomorphic corolla that is basally adnate to the androecium. The syncarpous gynoecium matures to form either a capsule, a schizocarp or a berry.
Thus, the correct answer is option A.