The answer is C.
First, we arrange the given observations in ascending order as follows.
22, 34, 39, 45, 54, 54, 56, 68, 78 and 84
Here, total number of observations, n = 10
Since n is even, we use the formula for the median.
Median=(n2)th observation+(n2+1)th observation2
=(102)th observation+(102+1)th observation2 [put n = 10]
=5th observation+6th observation2=54+542=1082=54
Hence, the median of given data is 54.