动物免疫血清的除菌宜采用 A．高压蒸汽灭菌 B．干烤 C．滤过除菌 D．紫外线 E．

等腰三角形的腰长为20，底边长为32，则其底角的余弦值是______．

电子水准仪使用的条形码尺都是印制在铟瓦合金条上。( )

翻译句子

1. She made several perchases in the dress shop. 

2. They've just perchased a new house in the country.

3. If' you are not satisfied with your purchase, you will get a full refund.

什么是高速公路的机电系统？

书法的起源？