_ difficult and challenging the task may be, wemust finish it on time, because there is a possibility _______our work will godown in history

The water supply has been cut off temporarily because the workers________one of the main pipes (2013·天津，13)

Can you believe _______little children can finish ______ difficult problems in______ a short time—I can’t believe it until I see it with my own eyes.

Jim passed the final exam, ___________ surprised his classmates and parents.

He is _________ of the three.