皮皮学，免费搜题
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搜题
【单选题】
钼酸铵分光光度法测定水中总磷时，磷标准贮备溶液在玻璃瓶中可贮存至少( )个月。A.
2 月
B.
4 月
C.
6 月
D.
8月
拍照语音搜题，微信中搜索"皮皮学"使用
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皮皮学刷刷变学霸
举一反三
【单选题】PSAs are often run _____ free, and are ______ to educate people about health, safety, or any other problem that affects public welfare.
A.
for, mean
B.
for, meant
C.
of, to mean
D.
in, meaning
【单选题】PSAs are often run for free, _____ to educate people about health, safety, or any other problem that affects public welfare. [ ]
A.
meaning
B.
meant
C.
to mean
D.
having meant