What _______ public is concerned about is whether medical workers and scientists will be able to find _______ cure for this new disease after the vaccine is tried on _______ volunteers.
Only when I left my parents for Italy _______ how much I loved them.
It was not until midnight _________ they reached the camp site.
— Did you meet with the famous space hero? — ___________ I had come here earlier.
The committee ______ five famous scientists put forward a valuable plan at the end of conference.
They suggested that the library ________ open during the vacation.