题目

After he retired from office, Rogers _____ painting for a while, but soon lost interest. A. took up      B. saved up     C. kept up      D. drew up 答案：A紫外线光子的动量为．一个静止的O3吸收了一个紫外线光子后（ ）A．仍然静止B．沿着光子原来运动的方向运动C．沿光子运动相反方向运动D．可能向任何方向运动