The fruiting body (ascocarp) of Penicillium is

The correct option is Cleistothecium.

In fungi belonging to the subdivision Ascomycotina (sac fungi), the sexual reproduction phase results in the formation of a fruiting body called an ascocarp, which contains the sac-like structures called asci (singular: ascus).
Depending on their structure and how they release spores, ascocarps are classified into different types:

1. Cleistothecium: This is a completely closed, spherical fruiting body with no natural opening (pore or ostiole). The asci are scattered inside, and the spores are released only when the outer wall (peridium) decays or ruptures. Penicillium and Aspergillus characteristically produce this type of closed ascocarp.

2. Apothecium: This is an open, cup-like or saucer-shaped fruiting body where the spore-bearing layer (hymenium) is fully exposed at maturity (e.g., in Peziza).

3. Perithecium: This is a flask-shaped fruiting body with a small terminal pore called an ostiole through which the ascospores are discharged (e.g., in Neurospora or Claviceps).

Therefore, because Penicillium forms a completely closed spherical ascocarp to house its asci, its fruiting body is classified specifically as a Cleistothecium.