Solution

A. in Corymb's main axis is short. Lower flowers are having long pedicles than upper ones. It is a type of racemose inflorescence such as in Iberis.

B. In Umbel, the main axis is very much reduced and all flowers appear to be arising from the same point. At its base the cluster of bracts forming an involucre.

C. In this type of racemose inflorescence, the main axis remains elongated with the older lower flowers.

D. Capitulum or head bears many sessile with small florets. The main axis is flat and called as a receptacle. It is a type of racemose inflorescence as in the sunflower.

So, the correct answer is D.