Bright and Dark Fringes Are Seen on a Screen When

Bright and dark fringes are seen on a screen when light from a single source reaches two narrow slits a short distance apart. The number of fringes per unit length on the screen can be halved

A) if the distance between the slits is changed to
.
B) if the wavelength is changed to
.
C) if the distance between the slits is
the wavelength is changed to
.
D) if any of the above occurs.
E) only if the width of the slits is changed to
.