酶褐变的关键作用因子有（）、酶和氧气。
参考答案：酚类底物
2011年我国在校小学生116897000人，改写成用亿作单位的数是______人，省略亿位后面的尾数约是______．
He was the new invention and asked the scientist about it over and over again. [ ]
A. curious about
B. angry with
C. friendly to
D. strict with
