用所给词的适当形式填空  (每空2分，共10分)
There_________ (use) to be a lot of manatees.
So far, no man____ (travel) farther than the moon.
How long ______ you ______ (be) in Ningxia? 
If it________ (be)a nice day tomorrow, we can go out for a picnic.
The aggressive animals should _______ (put) in cages.