锅炉效率试验负荷要求在70%额定负荷以上，试验煤种必须为设计煤种。（）
参考答案：错
解析：80%、为常用煤种或接近设计煤种
He spent as much time as he could ______ his spoken English. [ ]
A. improve
B. improving
C. to improve
D. improved
制备蜜丸时，一般药粉与蜜的常用比例为
A．1:0.5B．1:0.8C．1:0.9D．1:1～1:1.5E．1:2
