So difficult _______it to work out the problem that I decided to ask Tom for some advice.
I think this software is of little use to your work. It is really a ________ of money.
It’s said that this kind of plant only gives off this strange perfume on ________ conditions which the scientists are trying to figure out now.
As we know, success often comes after ______ failure; so don’t be so upset about _______ failure of this matter.
不填; the
It’s crazy of you to spend more time playing computer games than you _______ studying.
--Do you think you can finish the project by five o’clock this afternoon? ---_______. I’ll be busy with my term paper all day.