题目

The arts，especially music，should be part of every school's lessons at every grade level.Students would be much smarter if they had some musical experience.They could improve their classroom skills，like paying attention and following directions.People develop all these skills when they learn music.Making music also lets children use their imagination.It provides students with a chance to try out their own ideas.Music not only makes children better students，but also gives them something positive to do.In a music program，children can be part of a band instead of joining a gang(团伙)3．已知函数f（x）=ax3+3x2+1，若至少存在两个实数m，使得f（-m），f（1）、f（m+2）成等差数列，则过坐标原点作曲线y=f（x）的切线可以作（　　）A．3条B．2条C．1条D．0条