The correct option is A (1,1,√2)
The plane's equation in the intercept form is
x1+y1+zc=1
So, direction ratios of the normal are (1,1,1c) and that of the given plane are (1,1,0)
⇒cosπ4=1⋅1+1⋅1+1c⋅0√1+1⋅√1/c2+1+1
⇒1√2=2√2⋅√1/c2+1+1
⇒1c2+2=4⇒c=±1√2
Therefore, direction ratios of the normal to the plane is (1,1,±√2)