The answer is B. estudiante.
The article preceding it, 'las', is the plural feminine article. 'estudiante' in the sentence is singular only, but it is gender neutral. 'son' is the third person plural conjugation of the verb 'ser'. 'inteligentes' is an adjective that would refer to plural subjects. To fix the sentence, change 'estudiante' to 'estudiantes'.
Stop
Down
Good
Bed
In
Do
Time
Wash
Stoking
Table
Night
Plates
Useful
What
Couch
theoretical
I’m not really sure about the last one
Ana eS una pintora I think itS that
