Question

Which verb best completes the sentence?

Either two chairs or a small sofa _______ in this space.

A.
fit

B.
fitted

C.
fits

Answer 1

Either two chairs or a small sofa fits in this space.

Answer 2

Either two chairs or a small sofa fits in this space.
The answer is (fits) because when a sentence has a conjunction like "or," you make the verb agree with just one of the nouns. 
A small sofa (fit/fits) in this space. So, it is (fits).