（ ） some mammals came to live in the sea is now known.

She heard a terrible noise, （ ） brought her heart into her mouth.

No one should blind himself （ ） the well-known fact.

The chemical factory was torn down （ ） protecting the environment.

Yon don’t have the right to blame me _____ being late， for I was busy typing your business invitations.

To be frank, （ ） is a great relief to have the task fulfilled in so short a time.

The two companies decided to （ ） on a project concerning animal cloning.

Do you mean this is the_____decision you have made after thinking for hours?

I certainly didn’t appreciate （ ） when I made mistakes.

After （ ） seemed ages, the newsman disclosed the facts.

As population increases, （ ）.

The engineer （ ） my father works is about 50 years old.