物体由静止开始做匀加速直线运动，它在第t秒内的位移是s，则该物体的加速度可表示为（ ）．
物体由静止开始做匀加速直线运动，它在第t秒内的位移是s，则该物体的加速度可表示为（ ）．
表示
某元素B的核电荷数为Z．已知Bn－Am＋的核外具有相同的电子层结构；则A元素的原子序数用Z、n、m来表示，应为（ ）．
某元素B的核电荷数为Z．已知Bn－Am＋的核外具有相同的电子层结构；则A元素的原子序数用Z、n、m来表示，应为（ ）．
Lucy got to the station _____ late to catch the train, so she had to wait for the next one.
Lucy got to the station \_\_\_\__ late to catch the train, so she had to wait for the next one.
—What has _____ the boy who fell off the bike?—Nothing serious. The doctor says that he can come back to school in a day or two.
—What has \_\_\_\__ the boy who fell off the bike?—Nothing serious. The doctor says that he can come back to school in a day or two.
在同温同压下，A气体是同体积氢气质量的8.5倍；B气体对空气的相对密度为0.9．求A、B两种气体的相对分子质量．
在同温同压下，A气体是同体积氢气质量的8.5倍；B气体对空气的相对密度为0.9．求A、B两种气体的相对分子质量．
I am very _____ to you for your help.
I am very \_\_\_\__ to you for your help.