over
at
on
of
第1题：
determined
discussed
argued
sold
第2题：
How trees help prevent droughts and floods.
The relationship between trees and man.
How an empire fell to pieces in ancient times.
A story of trees.
第3题：
are; are
are; is
is; is
is; are
第4题：
to get
for getting
getting
got
第5题：
any time possible
when necessary
whenever possibly
whenever possible
第6题：
How trees help prevent droughts and floods.
The relationship between trees and man.
How an empire fell to pieces in ancient times.
A story of trees.
第7题：
The all dates of
The dates of all
The dates of each
Whole the dates of
第8题：
New trees are not looked after properly.
Many trees have been cut down by man.
Man has not paid enough attention to planting trees.
All of the above.
第9题：
Through experiment that
Through experiment it was
It was through that experiment
It was through experiment that
第10题：
administration
construction
management
institution