A:Yes, madam, on the second shelf over there.
B:The oranges are very cheap.
C:You like apples, don’t you?
D:Of course, we have some fruits.
小阳设计一个天然气泄漏检测电路,如图甲所示,R为气敏电阻,其阻值随天然气浓度变化曲线如图乙所示,R0为定值电阻,电源电压恒定不变.则下列说法正确的是( )
对下列两个生物概念模型的理解或者分析错误的是( )
计算 的结果为____.