坝垛抢险原则是什么？
参考答案：
坝垛抢险原则是护土固根。
He likes music very much and I often see him _________ music. [ ]
A. hear to
B. listen to
C. to hear
D. to listen
下列药物中，不需要单独粉碎的是
A．贵重药材
B．毒性药材
C．氧化性药物
D．含脂肪油丰富的药材
E．含大量胶树脂的药物
