Which is the destructive interference formula for diffraction grating problems?

For destructive interference from adjacent slits, the path difference must be a half-integer multiple of the wavelength: (n + 1/2)λ. In a diffraction grating, the path difference is d sin θ, so the condition is d sin θ = (n + 1/2)λ. This is choice B; d sin θ = nλ describes constructive interference.

AI-written and checked against the verified answer.