【多选题】某矿石由前 20 号元素中的 4 种组成,其化学式为 WYZX 。 X 、 Y 、 Z 、 W 分布在三个周期,原子序数依次增大, W 、 Y 为金属元素, X 原子的最外层电子数是次外层电子数的 3 倍, W 能与冷水剧烈反应, Y 、 Z 原子的最外层电子数之和与 X 、 W 原子的最外层电子数之和相等, Y 、 Z 位于同周期, Z 单质是一种良好的半导体。下列说法正确的是 ( )
【简答题】定语从句与状语从句 Directions: For each statement there are 4 choices marked A. B. C. and D. You are required to choose the correct answer. 1. He attended school in England for several years, after ____ he ret...
【简答题】Complete each of the following sentences wilh the proper form of the word given in bracket. (save) When the doctor returned from America. he used his _____to buy a flat in Beijing. 2. (scholar) My...
【简答题】After listening: Complete the following statements according to what you have heard. 1. The young store-keeper added up the items once more, because he was not feeling quite sure as to ( ...