题目

HowI Turned to Be Optimistic I began to grow up that winter nightwhen my parents and I were returning from my aunt’s house, and my mother saidthat we might soon be leaving for America. We were on the bus then.I was crying, and some people on the bus were turning around to look at me. Iremember that I could not bear the thought of never hearing again the radioprogram for school children to which I listened every morning. I do not remember myself crying forthis reason again. In fact, I think I cried very little when I was sayinggoodbye to my friends and relatives. When we were leaving I thoug已知f（x）=（a+1）x2+3x+1，若函数f（x）在区间（0，1）上恰有一个零点，则a的取值范围为（　　）A．a＜1B．a＞-6C．a＞0D．a＜-5