如果()氢化,则()中断,故二氢黄酮醇()色。
参考答案:双健;交叉共轭体系;无
Think and write. 写出下列答语的问句。
1. —
—I'm 12 years old.
2. —
—He's 136 cm tall.
3. —
—She likes swimming.
4. —
—She is 31 kg.
5. —
—I'm a student.
修一条10千米的路,甲队单独修要8天,乙队单独修要12天.现在两队合修需要几天完成?