题目

阅读下面的短文，从短文后各题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项。 Washoe is ayoung chimpanzee. She is no 1 chimpanzee, though. Scientists are doing aresearch 2 her. They want to see how civilized (驯化) she can 3. Already she does many things a human being can do.For example, she has been learning how to exchange 4 with people. The scientists are teaching her 5 language. When she wants to be picked 6,Washoe points up with one finger. She rubs her teeth with her finger 7 she wants to brush her teeth. This is doneafter every meal. W（2015秋•吉安期中）已知：矩形ABCD的两边AB，AD的长是关于x的方程x2﹣mx+﹣=0的两个实数根．（1）当m为何值时，四边形ABCD是正方形？求出这时正方形的边长；（2）若AB的长为2，那么矩形ABCD的周长是多少？