我们常用“水滴石穿”来说明一个人只要持之以恒地做某件事，就一定能成功．经测算，当水滴不断地滴在一块石头上时，经过10年，石头上可形成一个深为1厘米的小洞，那么平均每个月小洞的深度增加多少米？（结果保留三个有效数字，并用科学记数法表示）

B

    I have a twin brother, Bob. He is taller than me. His hair is shorter than mine. Many people think we must have many things in common. But in fact this is not true. Bob is more outgoing than me. When my parents' friends come to our house, Bob often sits there and talks to them. But I often sit there and say nothing. Bob likes reading, cooking and drawing. I just like swimming and playing basketball. He has more hobbies than me, but he is not as athletic(擅长运动的) as me. Because Bob does better than me at school, my mom often says to me, “Bob is younger than you, but he can get better grades, you should learn from him.” We both like eating fast food and listening to music.