_________ difficult and challenging the task may be, we must finish it on time, because there is a possibility _________we’ll be fired if we can’t fulfill the task on time．

Engineering is ______ challenging course of study that requires ______ thorough understanding of mathematics and science.

A. the; a        B. a; the     C.不填；不填            D. a; a

_______ difficult and challenging the task may be, we must finish it on time, because there is a possibility _______our work will go down in history.

A. Whatever; that           B. However; as

C. Whatever; which       D. However; that

_______ difficult and challenging the task may be, we must finish it on time, because there is a possibility _______our work will go down in history.

A. Whatever; that           B. However; as

C. Whatever; which       D. However; that

Many parents __________ challenging conversations with their children later this month to help them recover from the panic.

A. have had           B. will be having             C. have             D. will have had