问题
Have you ever seen any trees ________ leaves were black because of the polluted air?
A:whose
B:that
C:which
D:who
B:that
C:which
D:who
正确答案是：
同类题型
Tom, your father is waiting ______ you at the school gate.
Every possible means ______ to prevent the air pollution, but the sky is still not clear.
“Can you go hiking with us this Sunday” “Sorry , ________”
However, at times this balance in nature is disturbed, ____ a number of possibly unforeseen effects.