We have to identify the possible interval that describe an estimation of the population mean from the sample mean of 52.
When we estimate from a sample mean, the value of the sample mean will be at the center of the confidence interval: the boundaries of the interval will be equally distanced from the sample mean.
A simple way to check is that the average between the boundaries has to be equal to the sample mean.
For (50,60) the average is (50+60)/2 = 110/2 = 55.
For (48,56) the average is (48+56)/2 = 104/2 = 52, so it does match the sample mean.
For (42,58) the average is (42+58)/2 = 100/2 = 50.
For (40,62) the average is (40+62)/2 = 102/2 = 51.
The only interval with an average that matches the sample mean is (48,56).
Answer: (48, 56)