In a trapezium ABCD, AB is parallel to DC. If angle B is equal to 60 degrees and angle D is equal to 100 degrees, then what is the measure of angle A and angle C?
A. Angle A = 80 degrees, Angle C = 120 degrees
B. Angle A = 120 degrees, Angle C = 80 degrees
C. Angle A = 100 degrees, Angle C = 60 degrees
D. Angle A = 60 degrees, Angle C = 100 degrees