The correct option is A Monoadelphous
If the filaments of the stamens are fused in a single group the condition is known as monoadelphous. The stamens in a flower are collectively called as androecium. The androecium in various species of plants form a great variety of patterns, some of them highly complex. It surrounds the gynoecium and in turn the perianth, if there is one, surrounds the androecium.
Therefore, the correct answer is option A.