（75） involves comparing actual or planned project practices to those of other projects to generate ideas for improvement and to provide a basis by which to measure performance. These other projects can be within the performing organization or outside of it, and can be within the same or in another application area.

A．Metrics

B．Measurement

C．Benchmarking

D．Baseline

某机电安装工程公司承担了某制造厂的组装焊接工程。焊接前为减少焊接应力要求采取预热措施并提出了预热方法，焊接后采用自动控温的火焰加热装置进行整体热处理。该项目应遵循的原则为：①母材的性能、种类和焊接结构的特点及生产条件等诸多因素综合考虑，选择合适焊接方法，以保证焊接接头具有与母材相匹配的性能，满足产品的技术要求和质量要求；②考虑施工现场的实际情况，尽可能选择优质低耗、劳动强度低的焊接方法；③经过业主的质量检测。

下列的检查方法中，（）不属于致密性试验方法。

A．通球试验

B．煤油试漏

C．氨气试验

D．氦气试验