Not until then ________ how important the brakes were.

If nature does not provide man with the necessary material, it is the laboratory ____ he will turn to for it. [ ]

When did your cousin begin to show his interest in medicine?—It was a Saturday ___ she noticed her uncle experimenting on a frog in his lab

Will you help me make a shopping list(购物清单)– .

lice tried toget some clues from the suspect, but he rem