In the ______ house the firefighters saved a lot of______ people, but they couldn’t be sent to hospital because of the______ road.

A．damaged; blocked; injured

B．destroyed; damaged; blocking

C．damaged; injured; blocked

D．blocked; wounded; injured

气相色谱法定量分析时采用内标法的优点是

A．优化共存组分的分离效果
B．消除和减轻拖尾因子
C．内标物易建立
D．消除仪器、操作等的影响，优化测定的精密度
E．操作方便