Verbal Reasoning - Mental Ability Questions

Yes, a square is a rhombus. But a rhombus is not a square unless the interior angles are at right angles.

We know that, a square is a quadrilateral with all sides equal and all the interior angles are 90 deg i.e, at right angles. 

Whereas

a rhombus is also a quadrilateral with all sides equal but the interior angles are not at right angles. Hence, if the interior angles of a rhombus are all at right angles (90 deg), then it is square.

A compound sentence is a sentence that has at least two independent clauses joined by a comma, semicolon or conjunction. An independent clause is a clause that has a subject and verb and forms a complete thought.

Here except option A) other two options dependent.

Hence, A) We can go see a movie, or we can get something to eat is a compound sentence.