In January , 2004, the United States successfully launched “Spirit”, a Mars Exploration Rover, _____ a new milestone in the history of mankind. A. it marked B. marking C.
―Three _____ injured students died in a hospital ineast China's Jiangsu Province last year. ―Sorry to hear that. But our government ______ much about the school bus safety management. A.
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＜α＜2kπ+
，k∈Z
≤α≤kπ+
，k∈Z
,即-
≤sinα≤
≤α≤kπ+
，k∈Z