题目

The hemlock(铁杉) trees along the Wappinger Creek, New York, look healthy. However, scientist Gary Lovett says the white balls which provide protection for the bugs are created by a tiny insect. It’s hard to believe the tiny bug could kill a tree. However, trees can end up with millions and millions of the pests. When there are that many, it ends up killing the tree.The bug from East Asia is slowly killing trees across the USA. The trouble-making bug is just one of many invasive(入侵的) pests that have slipped into the United States. They can hurt other living things in their new home.M人进行呼吸时，呼出的（　　）A．是不含氧气的混合气体B．全是二氧化碳气体C．是氧气减少、二氧化碳增多的混合气体D．是氮气减少、二氧化碳增多的混合气体