Let x, y, z, a, b, c be the attributes of an entity set E. If {x}, {x,y}, {a,b}, {a,b,c}, {x,y,z} are superkeys then whichof the following are the candidate keys?

A

{x, y} and {a, b}

B

{x} and {a, b}

C

{x, y, z} and {a, b, c}

D

{z} and {c}