题目

阅读理解 There are many wetlands in China and some of them have become the world's important wetlands. The Chinese Yellow Sea Wetlands are among them. They are in Yancheng, Jiangsu Province. They are home for many different kinds of birds and animals. The world's largest Milu Deer Nature Reserve(自然保护区) is in them. More than700 milu deer live freely there. There are not many red—crowned cranes in the world, but every winter you can see some in the Red—crowned Cranes Nature Reserve in the Yellow Sea Wetlands. The temperature in the wetlands is usually neither too high nor too lIt was in the 1990s _______ we were working together ____ we made friends with each otherA.that; whenB.when; thatC.that; thatD.when; when