如果弯管程序中有转角，哪些转角度数，在什么条件可用目测的方法检查转角的准确性（）的都

转基因生物有益无害．______．

Strong sandstorms are often _____ you cannot see the sun.

A．so thick that

B．such thick that

C．thick in order that

D．thick such that

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（71） frequencies available for use at any time in the specified range. Devices using（72） spread spectrum (DSSS) communicate by （73） each byte of data into several parts and sending them concurrently on different （74） . DSSS uses a lot of the available （75）, about 22 megahertz (MHz).

73（）

A．splitting

B．combining

C．packing

D． compacting

下列符合化学实验“绿色化学”思想的有[ ]

①在萃取操作的演示实验中，将CCl₄萃取溴水改为CCl₄萃取碘水

②在铜与浓硫酸反应的实验中，将铜片改为可调节高度的铜丝

③将实验室的废酸液与废碱液中和后再排放

A．①②

B．①③

C．②③

D．①②③

某地北极星高度角为35º，同一天北极点正午太阳高度角为20º，该地正午时成都20点整。则该地气候类型为（）

A、亚热带季风气候

B、温带海洋性气候

C、地中海气候

D、热带沙漠气候