立交桥上一般都是单向行驶，车辆不必减速行驶。
参考答案：错
Questions 19 to 22 are based on the conversation you have just heard.
A．See more of her.
B．Spend more time in school.
C．Earn more money.
D．Get better grade.
为什么要建立营养需要动态模型？有何理论基础？
