题目：
选择适当的词填空。
1. Be (careful, careless) crossing the road.
2. Videos are (useless, useful) to have in the classroom.
3. Smoking is (harmful, harmless) to your health.
4. He comes in with (noisy, noiseless) footsteps (脚步) to surprise her.
5. It is (meaningless, meaningful) to chat (聊天) on the line because no one will say the truth.
6. She is a nice lady. It's (hopeful, hopeless) trying to convince (说服) her.
7. I'm afraid the news isn't very (cheerful, cheerless).
8. Water is a (colourless, colourful) liquid (液体).
答案：
1. careful
2. useful
3. harmful
4. noiseless
5. meaningless 
6. hopeless
7. cheerful
8. colourless
