In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.
Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz).

A．splitting

B．combining

C．packing

D．compacting

大脑半球病变的一般表现应除外（）

A．记忆的损害

B．智能和行为异常

C．激惹和技能的丧失

D．注意力的丧失

E．剧烈头痛