If `{:[(alpha,beta),(gamma,-alpha)]:}` is to be the square root of two-rowed unit matrix, then `alpha,beta and gamma` should satisfy the relation
A. `1+alpha^2+beta gamma=0`
B. `1-alpha^2-beta gamma=0`
C. `1-alpha^2+beta gamma=0`
D. `alpha^2-beta gamma -1=0`