■ 专项训练
    1. _____ he has limited technical knowledge, the old worker has a lot of experience.
    a. since b. unless
    c. as  d. although
    2. we thought there were 35 students in the dining hall, _____, in fact, there were 40.
    a. while b. whether
    c. what d. which
    3. ___________ environmental damage is done, it takes many years for the ecosystem（生态系统） to recover.
    a. even if  b. if only
    c. while  d. once
    4. “you can’t have this football back _______ you promise not to kick it at my cat again,” the old man said firmly.
    a. unless  b. since
    c. when  d. until
    5. i grew up in africa ______ at least i should say that i spent much of the first ten years of my life there.
    a. and  b. or
    c. so   d. but
    6. the cost of living in glasgow is among the lowest in britain, _______ the quality of life is probably one of the highest.
    a. since     b. when
c. as       d. while
    7. a man cannot smile like a child, ________a child smiles with his eyes, while a man smiles with his lips alone.
    a. so       b. but
c. and      d. for
    8. _____ you’ve tried it, you can’t imagine how pleasant it is.
    a. unless  b. because
c. although  d. when
    9. he found it increasingly difficult to read, ____ his eyesight was beginning to fail.
a. and  b. for  c. but  d. or
    10. start out right away, ____ you’ll miss the first train.
    a. and  b. but  c. or  d. for