Connecting link between annelida and mollusca is
Neopilina
Animal exhibiting characteristics of two adjacent taxonomic groups are called as connecting links.
Neopilina is the connecting link between annelida and mollusca.
Neopilina is the only segmented mollusc. It has a cup-shaped shell like that of a limpet. Its visceral mass is divided into five segments, each with a pair of shell muscles, gills, auricles and nephridia.
So, the correct answer is 'Neopilina'.