The correct option is
D Bottle Brush
A. The spadix is a spike with the fleshy axis and having both male and female flowers. It is a type of racemose inflorescence. The example is a banana.
B. Catkin is a pendulous spike in leaf axis which bears unisexual flowers. It is a type of racemose inflorescence. The example is mulberry.
C. Spikelet is a small and special spike. Flowers are produced in the axil of fertile bracts called lemma. It is a type of racemose inflorescence. The example is wheat.
D. Spike in which peduncle has bisexual and sessile flowers. It is a type of racemose inflorescence. The example is a bottle brush.
So, the correct answer is 'Bottle Brush'.