题目

 Pine trees, of which there are almost one hundred ____, are found throughout the North Temperate Zone.        A. species                     B. samples                    C. specimens   D. Standards 答案：A对“运动状态的改变”的正确理解是（　　）A、是指物体加速度的改变B、是指物体速度的改变C、是指物体位置的改变D、是指物体速率的改变