Which of the following single slit diffraction experiments has the smallest size of the angle from the center of the diffraction pattern to the first dark fringe? （ ）
选项：

A:wavelength 400 nm, slit width 0.20 mm;
B:wavelength 600 nm, slit width 0.20 mm;
C:wavelength 400 nm, slit width 0.30 mm;
D:wavelength 600 nm, slit width 0.40 mm.