Venus, Earth, and other planets also perturb Mercury's motion.金星, 地球和其他行星也使水星的运动受到摄动.Stellar passings can perturb the orbits of comets.行星的运行会使彗星的轨道发生扰动....
Lunar craters can be plainly seen with the aid of a small telescope.借助小型望远镜可以看清月球上的环形山.A series of collapse craters , or calderas, lie at its summit.其顶端有一系列崩塌的火山口, 或称火山臼.Tropical plants, sandy desert, waterfalls, craters...
He used elective system, replacing the stereotype of classical courses, students can pursue their professional interest.他采用选修制, 取代了刻板的古典课程, 学生们可以攻读他们感兴趣的专业.We is replacing all our salaried staff with freelancers.我们正在将所有领...