惰性气体不活泼，是因为原子的最外层电子数目是8，化学性质稳定。
参考答案：对
当m=______时，方程（m-3）xm2-m-4+mx-8=0是一元二次方程．
He looks thin, but he is _____ than before. [ ]
A. thinner
B. more thin
C. more strong
D. stronger
