Step 1: Fungi are grouped as Fungi Perfecti when both sexual and asexual stages are known, and as Fungi Imperfecti (Deuteromycetes) when only the asexual conidial stage has ever been observed.
Step 2: Parmelia, Neurospora and Taphrina all have documented sexual stages producing ascospores in asci, placing them firmly among the true Ascomycetes.
Step 3: Cercospora is the classic textbook example of a fungus known almost entirely by its conidial anamorph, with no confirmed sexual teleomorph in traditional classification, so it is grouped under Deuteromycetes.
The correct answer is Cercospora.