We are given the histogram.
Recall that a histogram is a graph that summarizes in some way, the amount of data we have according to its values. Recall that we are told that the histogram shows how many pages Alba reads each day of a month. So, for example, if at day one she reads 50 pages, then we have the data point
day 1 -----> 50 pages
if at day 2 she reads 2 pages, then we have the data point
day 2 ----> 2 pages
So our data looks something like this
day number of pages
1 5
2 2
3 150
.... ...
so, each day is an observation. As we are measuring the number of pages, each observation has the unit of measurement to be pages (so statement D is true and statement C is false).
To determine how many observations we had, we simply add the heights of each showned column.
We have the following heights
column 1: 9
column 2: 13
column 3: 7
column 4: 1
column 5: 1
Total of observations: 9+13+7+1+1=31 observations
(this means that statement A is false and statement B is true).
From the data, we can see that the heigher the column, the more observations we have in that data range. As the graph shows, most of the data is accumulated in the first three columns. However, we do have some observations that are far apart from the rest of the data (columns 4 and 5). This datapoints receive the name of outliers. So if Alba wants to calculate a measure of center, she should use the median as it is less affected by the presence of outliers. (This makes statement E true and statement F false).