In young's double experiment the separation d between the slits is 2 mm, the wavelength ` lamda ` of the used is `5896 Å` and distance D between the screen and slits is 100 cm . It is found that the angular width of the angular width of the fringes is `0.20 ^(@)` . To increase the fringe angular width to `0.21 ^(@)` ( with same ` lamda ` and D ) the separation between the slits needs to be changed to

Options

A. `2.1 mm`
B. `1.9 mm`
C. `1.8 mm`
D. `1.7 mm`