He can hardly swim, _______? [ ]
A. couldn't he?
B. can't he
C. could he
D. can he
答案:D
南方某市,于夏秋季节中午前后,城市上空常常出现浅蓝色烟雾,不少居民纷纷诉说眼睛红肿、流泪、咽喉疼痛及咳嗽。在此种情况下,当地CDC应当急速检测大气中何种有害物质的含量()
A.SO
B.CO
C.NOx
D.总氧化剂或O3
E.颗粒物
条码光电扫描器能分辨条码符号中最窄单元宽度的0.4mm,此仪器属分辨率的扫描器()
A.高
B.低
C.中
D.不一定