The path difference between the two waves
`y_(1)=a_(1) sin(omega t-(2pi x)/(lambda)) and y(2)=a_(2) cos(omega t-(2pi x)/(lambda)+phi)` is
A. ` (lambda )/( 2pi )phi `
B. ` (lambda ) /( 2pi) (phi +(pi)/(2))`
C. ` (2pi )/( lambda ) ( phi -(pi)/(2))`
D. ` (2pi)/( lambda) phi`