6. A student asks, "If A = {a,b,c) and B = {b,c,d), why isn't it true that A U B = {a,b,c,b,c,d)?" What is your response?
Choose the correct answer below.

A. It is not true that A U B = {a,b,c,b,c,d) because AU B = {a,b,c,d). Elements are not repeated in sets.

B. It is not true that A UB= (a,b,c,b,c,d) because AUB=

C. It is not true that A U B = {a,b,c,b,c,d) because AU B = {b,c}.

D. It is not true that A U B = {a,b,c,b,c,d) because the union of two sets always consists of less elements than either of the sets.

Please show work.