1.They said when it is put on top of something, two things happen.
on top of在…上边;在…上方
There was an unappealing film of slime on top of the pond.
池塘表面有一层黏腻腻的污泥。
2.Just 10 to 20 square meters of this material on the rooftop could nicely cool down a…house in summer.
cool down(使)变凉;冷静下来
Cool down very gradually after working up a sweat.
大量出汗后要慢慢降温。











