The answer to your question is C.
Write them in order from least to greatest,
11.9, 12.0, 12.3, 12.4, 12.4, 12.5, 12.7,12.8, 12.9, 13.1, 13.2, 13.8
then eliminate one from each side until you find the middle one,
12.5, 12.7
you have two middle, so you find the middle number in between them.
12.6 is the median.
16.76 rounds off to 17
After the dot if it’s 1-4 then they it would’ve been 15
5-9 is 17