If he ________harder , he will catch up with us soon .

---What were you doing at this time last night? --- I _________ a phone call.

—It’s said the Nanjing Airport light rail_________ into service in two months. — That’s great! It will be fast to go to the airport.

---Don’t play soccer in the street. --- Sorry, I        do that again.

I am very sad that I ______ many chances in the last few years.