Why don’t you _____ to improve your English? [ ]

Where would you like to go on vacation, Jack?–I’d like to ________ the jungle because I like exciting vacations.

My sister isn’t in. ________ she comes back, I’ll let her call you back.

Is your father a doctor in No.2 Hospital?—No, he ___________ a farmer and now he is a driver.

How long have you been running ? —Since ______ .