Choose the correct answers

The train arrived while/ as soon as Elie was having lunch.

Choose the correct answers

We saw many beautiful birds while we ____ in the lake.

Choose the correct answers

____ she left the party, Jenny said goodbye to the host.

Choose the correct answers

People think that global warming ____ lots of problems in the future.

Choose the correct answers

___ fumes from these vehicles are serious air pollutants.

Choose the correct answers

Land pollution is responsible for damage done ___ natural habitat of animals.

Choose the correct answers

Too much use of electric lights in cities may ______ light pollution.

Choose the correct answers

I learned a lot about wildlife until/ after I visited Cuc Phuong National Park yesterday.