There are 3 black cards, 2 white cards, and 7 green cards, in a box. What is the least number of cards that you have to pull out to make sure that you will have a matching pair? Choose the most appropriate option:  A) 8  B) 4  C) 5  D) 12  E) 11
Since there are 3 colors, if you take 3 cards, you could still have 1 card per color and not have a match.   Therefore, upon taking the 4th card, you will definitely have a match since the 4th card will form at least a pair with the 1st 3   So 3+1= 
<gadget id="calculator">3+1</gadget>
<output>4</output>
4   Answer is 4
<result>B</result>
There are 3 black cards, 2 white cards, and 7 green cards, in a box. What is the least number of cards that you have to pull out to make sure that you will have a matching pair?