13　when的用法　Track13

（1）可引導限定性和非限定性定語從句，其先行詞必須是表示時間的名詞，如day，year，time等。when可用on which 來替換。
a.I'11 never forget the day when I met you.
b.I'11 never forget the day on which I met you.
c.I'11 never forget the day that I met you.（特別關注：此句中that用作關系副詞）
d.April Fool's Day is that special day of the year when you should play a joke on someone! Children's favorites are to put salt in the sugar bowl for Dad's morning coffee or put chalk on a desk chair at school so the teacher gets a white backside! But remember, if you play a joke after 12 at noon, YOU are the April Fool!
e.We will put off the outing until next week , when we won't be so busy.
f.March 10, 1876 was the day when (= on which) the first complete sentence was sent over a telephone.
g.My favorite season is spring , when the earth seems born again.
h.The day may soon come when we don't bother to go to office but just work at home.
i.This kind of solar cooker can be used only in the daytime ______the sun is shining.
A. when
B. as
C. while
D. since
正確答案：A。
（2）緊跟在時間名詞后邊的關系副詞，也可省去。
a.I'11 never forget the day I met you.
b.Most education experts today stress the importance of "life-long learning”. They point out that education never ends. It is a continuous process. The day we stop learning is the day when we die.
（3）注意：表示時間的先行名詞，若定語從句不是缺狀語，而是缺少主語或賓語，要用which或that來引導定語從句。因為用when來引導定語從句的前提條件是when在其引導的定語從句中作時間狀語。
a.I'11 never forget the time which I spent on campus.
which作spent的賓語。
b.I'11 never forget the day when we first met in the park.
when作時間狀語，修飾met。
c.The hours_________the children spend in their one-way relationship with television people undoubtedly affect their relationships with real-life people.
A. when
B. on which
C. that
D. in which
正確答案：C。
分析：這句話的定語從句中的謂語spend缺賓語，因此填入的關系詞要充當這一賓語，所以選C。