听力原文:W: Friendship Department Store. May I help you?
M: Yes, could you tell me when the store closes today?
W: We close at 7:30.
M: I see. And when do you open?
W: Nine o'clock on the weekend.
M: Fine. Thank you very much.
what's the probable relationship between the two speakers?
A.Receptionist and customer.
B.Waitress and customer.
C.Salesperson and customer.
D.Nurse and patient.
第7题
用邻菲罗啉分光光度法测定水样中的铁含量时,加入盐酸羟胺的目的是()。
A.调节酸度
B.掩蔽杂质离子
C.将Fe2+氧化为Fe3+
D.将Fe3+还原为Fe2+
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