Let's see if we can recreate the histogram from the description.
Time count
0.5 0
1 0
1.5 2
2 1
2.5 3
3 1
3.5 2
4 1
4.5 0
5 0
The mean is between 2.5 and 3 so that will definitely decrease with a data point that's less that that, as 0.5 is.
For 10 data points the median is the average of the 5th and 6th when sorted, and those are both 2.5. When the new point is added the median will be the 6th of 11 points, still 2.5 in this story.
Answer: B the mean will decrease