Unlike the fossil fuels of today, biofuels are renewable sources, which mean that they will not ____ easily.
Don’t leave the water ____ while you brush your teeth.
_____ and out of breath, we reached the top of the mountain and stopped _____ the beautiful scenery.
I don’t know whether you happen ____ it, but I’m going to study in the U.S.A. this September. A. to be heard B. to be hearing C. to hear D. to have heard
“Do you have anything more ______, sir?” “No. You can have a restordo something else.”
Both of my parents insisted _______ a computer for me, but I don’t think it is necessary.