154. Using renewable energy is a simple idea, but ______ we find it hard to put into practice.
24.He has ______the habit of taking notes while reading.
23. The writing brushes ____bamboo and animal’s hair.
22. In ______,people in that village were very poor.
21.I’m vey busy toady. ______,I have much work to do today .
I think I can fix the car on Wednesday. ______, you’ll have to wait till Friday.