It is dangerous to __________ in the forest,because you are easily lost.
Thanks for your help , I couldn’t finish the work in time .
He always prefers a bicycle rather than on a crowded bus .
I’m sorry you’ve been waiting so long , but it will be an hour David gets back .
Some wild animals _____ and killed at such a speed that they will disappear from the earth in the near future.
Special attention should be _____ to air pollution wherever the factory will be built.