2.exist vi. ____________________

Man can't ______without air.(没有空气人就不能生存)

火星上有生命吗？___________________________________________?

拓展：存在 n.________________

bring...into existence ____________________

come into existence=come into being ___________________

(1). An information bureau was brought _______existence to deal with inquiries.

(2) When did this world come _______existence?

n. ______________