Exploring ________ space is exciting, yet dangerous.There is _______need for both robots and humans for space exploration.

Who sings_________ of the three

“May I speak to your manager Mr. Williams at five o’clocktonight”— “I’m sorry. Mr Williams ________ to a conference by then.”

Why are you so tired these days–Well， I have___________ homework to do.

Give a hand if possible and these people in the flooded are as ________ our help. [ ]