已知平面内两个定点$A\left(-1,0\right),B\left(1,0\right)$，过动点$M$作直线$AB$的垂线，垂足为$N$.若${\left|MN\right|}^2=\overrightarrow{AN}·\overrightarrow{BN}$，则动点$M$的轨迹是（   ）

①汽车和汽油

②火车和飞机

③牛肉和羊肉

④牙刷和牙膏

— Two kilos, I think.

      Now，an Internet game became more and more popular. People can “farm” on a piece of “land” and “grow”，“sell”(卖)“vegetables”, “flowers” and “fruits” on the Internet. They can make some e-money and buy “houses”.
What do people think of this game? Here are, some ideas.
Harold：I think they don'like the real world and it is hard for them to face the real world.
Allan：Having fun together is the most exciting thing about it.
Laura：People are looking forward to the life in the village. It can help them understand the real world.
Ivy：It's just waste(浪费) of time. People will not focus on(专注于)their work or study if they spend too much time on it.