A.4*D B.A_B C.4ABC D.A+B
A.(x<=4)and(x>=6) B.(x>4)Or(x>6) C.(x>=4)Xor(x>=6) D.not(x<>4)
A.xy/b+c B.x*y\b+c C.x*y/(b+c) D.xy\(b+c)