在下列各数：﹣3，+8，3.14，0，π，$\frac{1}{3}$，﹣0.4，2.75%，0.1010010001…中，有理数的个数是（　　）

一般而言，探究活动起始于（  ）

    Fred is a bus driver. He always drives the number 14 bus. Fred's bus goes 1the shopping mall on High Street to the park on Queen Street, then 2to the shopping mall. Fred3work at six o' clock every morning.4 bus leaves the shopping mall at ten past six. Fred is sometimes5 to work. When he is early, he sits in his bus and6the newspaper until it's time to go. Fred always stops for 7on the bus because he has to finish work at three o'clock in the afternoon. He doesn't go home by bus. He 8 ! He thinks it's really good for his health. Fred loved his 9 because he can meet different people every day. And he is very10. So the people who travel on Fred's bus like Fred very much.

伞藻是单细胞藻类，由帽、柄、足3部分组成，细胞核位于足中。下图表示伞藻的嫁接实验。该实验结果表明