题目

A great number of students by the interviewer said that they were forced to practice the piano. A . to question B . to be questioned C . questioned D . questioning 答案：C某些花岗岩石材中含有放射性元素氡，一种氡原子的质子数为86，中子数为136，这种氡原子的核外电子数（ ）A．50B．86C．136D．222