患者有损害，在下列何种情形下，可推定医疗机构有过错（） A.违反法律、行政法规、规章

甲小学为了“六一”儿童节学生表演节目的需要，向乙服装厂订购了100套童装，约定在“六一”儿童节前一周交付。5月28日，甲小学向乙服装厂催要童装，却被告知，因布匹供应问题6月3日才能交付童装，甲小学因此欲解除合同。根据《合同法》的规定，下列关于该合同解除的表述中，正确的是()。

A.甲小学应先催告乙服装厂履行，乙服装厂在合理期限内未履行的，甲小淡定才可以解除合同

B.甲小学可以解除合同，无须催告

C.甲小学无权解除合同，只能要求乙服装厂承担违约责任

D.甲小学无权自行解除合同，但可以请求法院解除合同

以下哪一项不是PFM冠桥的金-瓷结合机制（）

A.范德华力

B.化学结合力

C.大气压力

D.机械结合力

E.压缩结合力

施工成本管理是利用组织、经济等措施，把成本控制在计划范围内，以寻求( )。

A．计划成本越低越好

B．最大程度的成本节约

C．计划成本的准确范围

D．确保能够降低成本

质子和中子统称为（）。

A.原子核

B.质量

C.核子

D.带电粒子

E.正电子

(1) is used to ensure the confidentiality, integrity and authenticity of the two end points in the private network. (2) , an application-layer protocol, authenticates each peer in an IPsec transaction. IKE negotiates security policy, determining which algorithm may be used to set up the tunnel. It also handles the exchange of session keys used for that one transaction.

Networks that use (3) to secure data traffic can automatically authenticate devices by using (4) , which verify the identities of the two users who are sending information back and forth. IPsec can be ideal way to secure data in large networks that require secure connections among many devices.

Users deploying IPsec can (5) their network infrastructure without affecting the applications on individual computer. The protocol suite is available as a software-only upgrade to the network infrastructure. This alows security to be implemented without costly changes to each computer. Most important, IPsec allows interoperability among different network devices, PCs and other computing systems.

1（）

A．Certificate

B．Encryption

C．Tunnel

D．Presentation