题目

—That's the third time he's won the award in this field．—Yes. He ______ his maximum potential in the past decade．       A. explored                                              B. is exploring       C. has been exploring                              D. had explored 答案：C下列关于粗盐提纯的操作中，正确的是（ ）A．把浑浊的液体直接倒入蒸发皿中加热B．开始析出大量晶体后用玻璃棒搅拌C．待水分完全蒸干后停止加热D．蒸发皿中出现大量晶体后停止加热