Explanation:

Correct Answer is (c).Sentence I. Mr. Batra wanted to make sure we were square with the court's decision and not subject to a lawsuit.
Here, the word ‘square’ means ‘compatible or in agreement’ and is absolutely correct.
Sentence II. After the party, Mohan and Meera decided to square up the bill.
In the above sentence, the verb ‘square’ means ‘to settle or pay (a bill or debt)’ and is correct as well.
Sentence III. We had been as square with the Startup as any Venture Capitalist could be.
In this sentence, the adjective ‘square’ means ‘fair and honest’ and is correct too.
Evidently, all the sentences are correct both grammatically and contextually.
Option E is hence the correct answer.