单项选择题
A.I/2B.I/4C.I/8D.I/16
A.1mB.0.5mC.2mD.1.5m
A.0.75λ;0.75λ/nB.0.75nλ;0.75λC.0.75λ;0.75λD.1.5λ;1.5λ/n