The first paragraph is engaged in ______.
A. describing several world famous cities in developing countries
B. illustrating the seriousness of environmental problems in developing countries
C. drawing a picture about the seriously polluted future world
D. comparing the pollution problems in developed and developing countries
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What is the most suitable title for this passage？
A. Freecycle Means Free Stuff and a Cleaner Environment.
B. A Very Useful Website.
C. A Good Way to Give and Get.
D. Freecycle Intends to Avoid Cabbage.
A．boilingB．toilingC．choppingD．cutting
A. boiling
B. toiling
C. chopping
D. cutting
有一条指令用十六进制表示为CD21，用二进制表示为()。
A. 1.10111e+015
B. 1.10011e+015
C. 1.10011e+015
D. 1.10111e+015
Small particles mainly damage ______.
A. lungs
B. eyes
C. bloodstream
D. heart
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