[单选题]
A monochromatic light beam of w m+*iizlh*,i7k( uh dkavei79dj +vxl(a:ckeo8gb tkryv196jm/length λ is diffracted at a single slit of width xk v9 aj9(r i j6lvbkey17+ocgm8:td/$b$. 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
