Which of the following clauses explains RESULT？A．It must be morning, for the birds are sin

Which of the following clauses explains RESULT？

A．It must be morning, for the birds are singing.

B．His plan was such a good one that we all agreed to accept it.

C．The boss asked the secretary to hurry up so that he could leave earlier.

D．We dare not play jokes on him lest that he should become angry.

请帮忙给出正确答案和分析，谢谢！