You have two boxes of colored pens. The first box contains a red pen, a blue pen, and green pen. The second box contains a yello
w pen, a red pen, and a black pen. What is the set that represents all the pens? A. {red pen, blue pen, green pen}
B. {red pen}
C. {red pen, red pen, green pen, yellow pen, black pen}
D. {red pen, blue pen, green pen, yellow pen, black pen}