t=0时刻一质点开始做初速度为零的直线运动，时间t内相对初始位置的位移为x． 如图所示， $\frac{x}{t}$ 与t的关系图线为一条过原点的倾斜直线．则t=2s时质点的速度大小为（   ）

根据短文内容，判断正误。符合短文内容，对的写正确，错的写错误。

    Ann and Lucy visit the zoo today. They see many animals there. Look, a bear is under the tree. You can see two pandas near the river. Ann and Lucy like pandas very much. There are two tigers and four leopards at the zoo. Some foxes, rabbits and squirrels are behind the rocks. Six sheep and eight goats are on the ground. They are eating grass. Ann and Lucy like all the animals at the zoo. They have a good time today.

世界三大人种不包括（  ）