-What's up? You look worried.Well,I_____on the problem for 5 hours but I haven't got a single clue.
The astronaut did many experiments in the spaceship,__________________much help for knowing space.
Once ____________ , a plan should be carried out.
—"How do you like the book?" — "It's quite different from I read last month."
He failed in the examination, ________ made his father very angry
I had _________good lunch at ________ restaurant __________ we met for the first time.