【单选题】The topic in the sentence “Air pollution in Beijing is due to a number of reasons” is__________.
A.
air pollution in Beijing
D.
the reason for air pollution
【简答题】每帮助一个好友领取淘金币,系统奖励你____金币,上限为(____/日)
【单选题】声波在介质中传播时,如果交界面两侧介质的声阻抗相差非常悬殊,则发生
【单选题】民事主体在民事活动中以自己的意志充分表达自己的意愿,这是民法的 ( )原则的体现:( )
【单选题】Last month, John arrived in Beijing __ . [ ]