What _______ public is concerned about is whether medical workers and scientists will be able to find _______ cure for this new disease after the vaccine(疫苗) is tried on volunteers.
I can't go to the park with you. ________, I don't want to go, ________ I don't have enough money.
The students __________ to follow the rules and study hard.
—Which one of these do you want?— __________. Either will do.
It was his first time to make a radio broadcast. __________, he walked towards the microphone.
—Did you enjoy yourself at the party?—Yes. I've never been to __________ one before.