-- I heard that there are a few seats left for tonight's show.
-- Really? I was under the impression ______ they were sold out a long time ago.
A：what
B：which
C：that
D：where
有资料表明，被称为“地球之肺”的森林正以每年15000000公顷的速度从地球上消失，15000000这个数用科学记数法表示应是（ ）
