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【单选题】

[Single-choice question] The nature of DNA denaturation means:

A.
The phosphate diester bond in the molecule breaks
B.
Polynucleotide chain depolymerization
C.
DNA molecule from superhelix to double stranded helix
D.
The hydrogen bond between the complementary bases breaks
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参考答案:
参考解析:
.
刷刷题刷刷变学霸
举一反三

【多选题】以下有关 AWS IoT中Device Shadow服务的说法,正确的有?

A.
设备可以将自己的状态信息发布到 Device Shadow中去,供应用程序或其他设备使用
B.
只有当设备与 AWS IoT处于连接状态时,用户才可以往Device Shadow中发布更新的状态信息
C.
Device Shadow用于存储和检索设备的当前状态信息
D.
Device Shadow设备影子是一种JSON文档

【单选题】下图受电弓为(      )

A.
单臂弹簧式受电弓
B.
双臂弹簧式受电弓
C.
单臂气囊式受电弓
D.
双臂气囊式受电弓

【单选题】______ for your help, we'd never have been able to get over the difficulties.

A.
Had it not                          
B.
Had it not been
C.
If it were not                      
D.
If we had not been