11. Lock up those chemicals __   _ the children should touch them.

    A. in order that     B. so that     C. until     D. lest

    12. An atom is so small__   _.

    A. that we can see it with a microscope

    B. as not for us to see it even with a microscope

    C. that we cannot see it even without a microscope

    D. that we cannot see it even with a powerful microscope

    13. __   _we can make laws to protect certain animals， we are frequently incapable of controlling the environment.

    A. However         B. Provided that    C. While      D. Whatever

    14. Rare animals are still hunted， __   _we can now imitate their skins with other products.

    A. when   B. ever since   C. so that   D. even though

    15. __   _convincing an argument is， it needs support of evidence.

    A. However    B. Whatever     C. Though     D. Even if

    16. __   _， he could not lift the weight.

    A. Strong while he was     B. However strong as he was

    C. Strong as he was        D. Strong although he was

    17. I'll get there __   _ I have to pawn my watch to get the railway fare.

    A. though     B. even if    C. since     D. once

    18. __   _I have heard the music I understand why you like it so much.

    A. Unless   B. Even though   C. Now that   D. In case

    19. __   _there is no opposition， we shall hold the meeting here.

    A. while    B. Ever since    C. Provided that   D. As soon as

    20. Anyone can borrow books from this library __   _ he keeps them clean and returns them in time.

    A. even if    B. unless     C. so that     D. as long as

    DDCDA CBCCD