用所给词的适当形式填空
1.There____ (use) to be a lot of manatees.
2.So far, no man____ (travel) farther than the moon.
3.How long ____you____ (be) in Ningxia?
4.If it____(be)a nice day tomorrow, we can go out for a picnic.
5.The aggressive animals should____ (put) in cages.