Given the sets A=a,bA = {a, b}A=a,b and B=c,dB = {c, d}B=c,d, what is the union A∪BA \cup BA∪B?
a,b{a, b}a,b
c,d{c, d}c,d
a,b,c,d{a, b, c, d}a,b,c,d
{}