The choice of Cr K alpha radiation and (211) plane to determine the stress of an iron specimen is because
选用Cr的Kα辐射和（211）晶面来测量Fe样品的应力是出于什么原因？
A、peak broadening can be easily noticed
因为衍射峰宽化容易观察到
B、the operating voltage for Cr target is relatively low
因为Cr靶的启动电压较低
C、the Bragg angle is sufficiently large
因为其布拉格角足够大
D、there is less absorption
因为吸收少