题目

While being shy is normal, it is when the shyness interferes with an individual’s daily communication with others ________ it becomes a disorder. A. which   B. when     C. where    D. that 答案：D一个直角三角形的两条直角边长是方程x2-7x+12=0的两个根，那么这个直角三角形外接圆的半径等于    ．