14) A thief spies on Marco while he locks his suitcase with a 3-digit combination lock (each digit ranges from 0 to 9). He couldn't see the combination, but he managed to figure out that two consecutive digits are the same and the third is different. What is the maximum number of combinations the thief will have to try to open Marco's suitcase?
(A) 180
(B) 190
(C) 200
(D) 210
(E) 220.
14) The answer is (A)

The number of combinations of the type $x x y$ with $y$ different from $x$ is $10 \times 9$ (10 choices for the digit $x$ and, for each of them, 9 choices for the digit $y$), and it is equal to the number of combinations of the type $y x x$. Therefore, the combinations are a total of 180.