【单选题】Ann:May I help you wash up,Mum?Mum:__________.
C.
Thank you,you’re so helpful
【单选题】标定溶液称取基准物应用 ______ 来称取。 A .粗天平; B .分析天平; 。
【单选题】—Good morning, sir. May I help you?rn—_______
A.
No, I don’t buy anything.
B.
No, I don’t need your help.
C.
I’m just having a look around.
【简答题】听力原文:F: Leisure Travel Agency, Mary speaking. How may I help you? M: Can I speak to Jack, please? F: I'm afraid he's out to lunch. Can I take a message? M: Yes, please. My name's Vicksin. F: That's V-...
【单选题】关于登革病毒的致病性和免疫性,下列哪项是错误的
A.
在自然界,登革病毒储存于人和猴体中,经伊蚊传播
C.
初次感染形成的抗体对机体有保护作用,可减轻再次感染的症状
D.
初次感染诱生的抗体对再次感染的病毒,可发生免疫促进作用
【简答题】某基准物A的摩尔质量为130g·mol -1 ,用来标定0.02mol·dm -3 的B溶液,该滴定反应为5A+2B====2C则每份基准物的称取量为 (A) 0.02~0.03g (B) 0.06~0.07g (C) 0.1~0.2g (D) 0.2~0.4g