根据句意和汉语注释，在答题卡标有题号的横线上，写出单词的正确形式。
1. Sometimes ____________（深厚的） feelings are hard to put into words.
2. Mr Wang was busy, but he ____________ （坚持） on seeing me off at the airport.
3. Will you join us in the ____________（讨论）about the teenage problems.
4. You can cross the road in ____________（安全）when the traffic lights turn green.
5. In the morning taking a walk and ____________（呼吸）some fresh air are good for your health.