To find the missing number in the sequence 54, 49, ?, 39, 34, we need to identify the pattern.

Looking at the given numbers, we can see that each subsequent number is obtained by subtracting 5 from the previous number.

Starting with 54: 54 - 5 = 49 49 - 5 = ? ? - 5 = 39 39 - 5 = 34

Therefore, the missing number in the sequence is obtained by subtracting 5 from 49, resulting in 44.

So, the correct answer is:

C. 44