植物细胞和动物细胞的主要区别？（）A.液泡 B.质粒 C.中心体 D.细胞壁

在手势指挥信号中，单手自然握紧置于头上，轻触头顶，是指挥要（）。

A、副钩

B、主钩

C、升臂

D、伸臂

休克肾

下面哪个因素不会影响选择反应（）。

A、遗传变异

B、选择强度

C、世代间隔

D、留种率

TCP/IP (71) layer protocols provide services to the application (72) running on a computer. The application layer does not define the application itself, but rather it defines (73) that applications need — like the ability to transfer a file in the case of HTTE In short, the application layer provides an (74) between software running on a computer and the network itself. The TCP/IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP/IP (75) layer consists of two main protocol options — the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

A. services B. processes C. applications D. address

按反馈成分分类，可分为（）

A.电压反馈和电流反馈

B.串联反馈和并联反馈

C.正反馈和负反馈

D.直流反馈和交流反馈