ANSWER
[tex]D)A\cup B=\lbrace3,5,6,10,12,13,15,21,25\rbrace[/tex]EXPLANATION
To find A ∪ B, we have to find the set of all the numbers that are contained in sets A and B.
Therefore, we have that:
[tex]A\cup B=\mleft\lbrace3,5,6,10,12,13,15,21,25\mright\rbrace[/tex]The answer is option D.