题干
Andy is content with the toy. It is _____ he has ever got.
A：a better
B：the better
C：a best
D：the best
答案(点此获取答案解析）
D
Andy is content with the toy. It is _____ he has ever got.
A：a better
B：the better
C：a best
D：the best
2NO＋O2，此反应达到平衡状态时的标志是( )