Let D be the set of all students in the class. Define the predicates: P(x): x studied, xD Q(x): x received an A, XED R(x): x received a B, xD Which logical expression states: "Everyone who studied either received an A or a B" a. VxED, Q(x) A P(x) A R(x) b. VxD, Q(x) v R(x) P(x) C. 3xED, P(x) - (Q(x) v R(x)) d. VxED, P(x) (Q(x) v R(x))