At a loss = puzzled or uncertain what to think, say or do; baffled. Hence, at a loss .... should be used.

Correct Option: B

At a loss = puzzled or uncertain what to think, say or do; baffled. Hence, at a loss .... should be used.

It is a preposition related error. Hence, of cholera .... should be used.

Correct Option: B

It is a preposition related error. Hence, of cholera .... should be used.

The structure of subject will be : Juan Carlos, the king of Spain.

Correct Option: A

The structure of subject will be : Juan Carlos, the king of Spain.

Whose is used to say which person or thing you mean. Look at the sentence : He is a man whose opinion I respect. Which is used to be exact about the thing you mean. Look at the sentence : Houses which overlook the lake cost more. Hence, whose money .... should be used.

Correct Option: B

Whose is used to say which person or thing you mean. Look at the sentence : He is a man whose opinion I respect. Which is used to be exact about the thing you mean. Look at the sentence : Houses which overlook the lake cost more. Hence, whose money .... should be used.

It is double superlatives related error. Hence, the tallest .... should be used here.

Correct Option: B

It is double superlatives related error. Hence, the tallest .... should be used here.