Which type of sentence asks a question and uses a question mark?
a.
declarative
b.
imperative
c.
nominative
d.
interrogative

An "interrogative" sentence asks a question. 

Allusion and illusion. an allusion is an indirect reference, whereas an illusion is something that is unreal or incorrect. each of the nouns has a related verb form: allude “to refer indirectly to,” and illude (not a very common word), which may mean “to delude or deceive” or “to subject to an illusion.”