问题
选择题
无脊椎动物区别于脊椎动物的特征是 [ ]
A．卵生
B．变温
C．无附肢
D．无脊柱
答案
答案：D
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无脊椎动物区别于脊椎动物的特征是 [ ]
A．卵生
B．变温
C．无附肢
D．无脊柱
答案：D
World Wildlife Fund (WWF)'s goal is to save the world's environment. The organization was set up ___21__September 11，1961. In the beginning, WWF worked __22__ the world's wildlife. Now, it works to save Earth__23___ its environment. WWF has many tasks. One is to stop air pollution. Pollution from industry(工业) and cars is _24_ to our environment. Each year, more and more trees are cut down __25__WWF tries to protect Earth's forests．Also people use more land, more and more animals are __26__ their homes and many die. WWF can buy important areas to __27__ the land from disappearing because of human development. WWF has completed many projects. In China, WWF works to save pandas from extinction（灭绝）． ___28__South America，it works to save the Amazon Rainforest. Volunteers and donations help WWF complete its work. WWF's work is __29__to our environment, and is also important for people to help them __30__ time and money.
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