跟着汉语写出短语。

设n_A代表阿伏加德罗常数(N_A)的数值，下列说法正确的是(　　)。

有一种兴奋剂的结构简式如右式，下列有关该物质的说法正确的是（   ）

阅读理解。
A
    How do you go to school?  
   Sally： My school is not far from my home. It is about three kilometers. I usually walk to school, but sometimes I go to school by bike.
   Nick： My mother usually drives me to school. But when Aunt Lucy is here, I walk with her. It takes me 7 minutes by car or 25 minutes on foot.
   Mary：I go to school on the school bus. The bus comes at 8: 35 am and I get to school at 8: 50 am. I love to take the school bus because my best friend Linda takes it with me. We have lots of fun.

_________ time and labor, cartoonists generally draw the hands of their characters with only 3 fingers and a thumb．