I’m concerned that by the time __________ 50 years old, most of the Arctic sea ice will have disappeared!

• I’m

• I’ll have been

Well, it’s certainly possible, as it __________ steadily for years by then.

• will probably have

  been melting

• has probably melted

And if that __________, our planet will have lost some important animal and plan habitats – with all the ice melting away.

• will have happened

• happens

Yeah, and if so, there’s a danger that many species __________ extinct.

• will have been becoming

• will have become

I know. We really ought to do something about it, so our children __________ that we didn’t try to stop it!

• won’t say

• won’t have said

A place where animals breed and __________ their young is called their breeding ground.

• mate

• raise

• nest

Some animals dig a hole, called a __________, for shelter.

• hatch

• burrow

• predator

Many species of birds build a nest in which they can __________ their eggs.

• lay

• burrow

• ground

A large group of penguins is called a __________.

• migration

• ground

• colony

Birds have to seat on their eggs to keep them warm until they__________.

• hatch

• mate

• lay