下边漫画启示我们（）
 

关于模拟通信和数字通信，说法不正确的是（　　）

“$\tan \alpha =1$”是“$\alpha =2k\mathrm{\pi }+\frac{\mathrm{\pi }}{4}\left(\mathrm{k}\in \mathrm{Z}\right)$”的（       ）

某位古希腊哲学家首次让哲学“成为探究生活和道德、善与恶所必须”的学问。这位哲学家是(    )

     Mrs Smith is Jim's mother. She loves her family very much. She often buys food, fruit and clothes for Jim and his father. Now many clothes are on sale at a good price.
     Mrs Smith comes to the store and she wants to buy some clothes. They have sweaters in all colors for￥15 each and sports shores for only ￥28.Mrs Smith likes the red sweater and  she buys one for herself(她自己).She buys a pair of sports shores for her son. The T-shirts in the store are just ￥18! She buys a white one for Mr Smith. And that's not all. The socks, in all colors, are ￥2 each. She buys five pairs.