[单选题]
A monochromatic light beam of wavelength λ is diffracted at a sing3a-8zbisexzr .-5e 49 vgmp sole7wa cgfgyolya do)0nr 476j;, slit of widthy w,6 gl7on 70gyrjadcof 4);a $b$. After passing the slit, a diffraction pattern is observed on a screen a large distance away. The width of the central maximum is $w$.
The screen is moved closer to the slit. Which of the following changes, done separately, could result in no change in $w$?
A. $b$ is increase;$λ$ is increase
B. $b$ is increase;$λ$ is decrease
C. $b$ is decrease;$λ$ is increase
D. $b$ is decrease;$λ$ is decrease
