The correct option is
B Mericarps
Carcerulus has a schizocarpic fruit and thus, it has many mericarps or single seeded indehiscent compartments.
Mesocarp is a part of pericarp of a fruit.
Achene is a type of fruit.
Cocci are dehiscent mericarps.
So, the correct answer is 'Mericarps'.