Is this ________ elephant or _______ lion?

How do you like the film AVATAR?–– Great! I _______ such a wonderful film before.

We _____ more than 1,600 words since we began to learn English.

I haven’t heard from Henry for a long time.—– What do you think ___________ to him?

Is that boy Alan?—No, it ______ be him. He left for Beijing yesterday.