胰岛素瘤是来源于胰岛什么细胞的罕见肿瘤()
A.D细胞
B.A细胞
C.PP细胞
D.G细胞
E.B细胞
参考答案:E
如图所示,R1=10欧姆,电流表A1示数为0.5安培,电源电压为10伏特.下列叙述不正确的是( )
A.R1和R2并联
B.R2阻值为20欧姆
C.R1两端电压为10伏特
D.电流表A的示数为1.0安培
In the short run, if price is below average total cost (ATC), the firm will:()
A. keep running as long as it is covering its variable costs.
B. produce more.
C. raise prices.