In a type of inflorescence a cup-shaped involucre encloses a single female flower in the center and a number of male flowers around this on short stalks. This type is called-

Cyathium is the correct answer. It's a specialized inflorescence found in Euphorbia species, characterized by a cup-shaped involucre (the cyathium) that contains a single central female flower (pistillate) surrounded by several male flowers (staminate) on short stalks. Capitulum is a flower head (like sunflower), Hypanthodium is a fleshy receptacle (like fig), and Verticillaster is a whorled inflorescence (like in Ocimum).