Daniel found ___ easy to finish writing the report on wildlife.

 -- Did you read a book about customs last week?-- Yes, I found ______ very useful to know the customs of foreign countries.

 Ted's mother kept telling Ted not to tell lies, but_______ didn't help.

 ---Tony, ________ is my good friend, Harry.--- Hello, Harry.

Scientists are working hard to make _______ possible for people to live on Mars in the future.