题目

 Here is a desk_____ wood.        A. made from     B. be made of   C. made of    D. be made from 答案：C一定温度下，将某硝酸钾溶液蒸发掉100g水，无晶体析出，再蒸发掉100g水，析出20g硝酸钾．此温度下硝酸钾的溶解度是（　　）A．一定等于20g/100g水B．一定不等于20g/100g水C．小于或等于20g/100g水D．大于或等于20g/100g水