闪烁计数器内的闪烁体常用的有()和CsI(Tl),其中加入少量的铊(Tl)作为激活剂用。
参考答案:NaI(Tl)
The Chinese mainland has 157 billionaires as of 2013,_________second in the number of billionaires worldwide.
A.having ranked
B.ranked
C.to rank
D.ranking
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