某人将一细菌培养物用紫外线照射后立即涂在加有链霉素（Str）的_爱下问搜题

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问题问答题简答题

某人将一细菌培养物用紫外线照射后立即涂在加有链霉素（Str）的培养基上，放在有光条件下培养，从中选择Str抗性菌株，结果没有选出Str抗性菌株，其失败原因何在？

答案

参考答案：

第一，紫外线诱变后见光培养，造成光修复，使得突变率大大下降，以至选不出Str抗性菌株。

第二，紫外线的照射后可能根本没有产生抗Str的突变。

完形填空

I used to work as a waitress in a little restaurant. I felt frustrated then so I had been   31 that period. I hadn’t told anybody except my employer. Somehow a   32  had overheard (无意中听到) my saying that I had to go to another   33 . As I passed her table, she   34  me a card with her phone number on it. She explained that she lived in Sydney and that I should call   35  I needed any help.
Some weeks later, it was time for   36  appointment(约会) in Sydney and I flew there. I was   37  as I had never been there before and didn’t   38  anyone else there. So I   39  to ring the lady who had given me her   40  number, even though I had only met her that once.   41  I had arrived, she was very excited and came   42  to meet me. She gave me a bed and a meal and took me to my appointment the next day and afterwards, she took me back to the   43 .
She treated me so   44  that I offered her a gift to express my   45  but she refused. She said “Your   46  to me is to offer your help to another when it is   47 .” Over the months we kept in touch but then for some reason our communication got less and less   48 .
I always felt I wasn’t giving enough to others as a   49 , but she had told me that I gave her very much and the way I   50  people was a gift. I now give a hand to others every day even if it is only a smile to those who have none to give.

A．going through

B．worrying about

C．wishing for

D．dreaming of

A．Considering

B．immediately

D．unwillingly

A．thankfulness

C．appreciated

C．talked about

多项选择题

商户和收银员的过失或欺诈行为将承担相关法律责任，主要包括（）个方面。

A.拒绝受理银行卡

B.向持卡人收取除货款外的刷卡手续费

C.分单操作等违反收单银行规定的行为

D.违反人民银行有关规章向持卡人提供套现服务

E.与伪卡团伙勾结，盗录银行卡磁条信息

F.以多刷卡、重复刷卡等方式侵占持卡人资金