The question says:

Land surveyors visited a small fishing village and divided the land into
plots,each 120 square meters in area.
They counted the number of
dwellings on each plot and recorded their data in the bar graph to the
left. Due to people moving away from the village,some residents are
now combining dwellings together in order to create larger ones.lf
this is the only change being made to the data,then which of the
following must be true when the land is surveyed again?
A)The mean number of dwellings will decrease.
B)The median number of dwellings will decrease.
C)The range of the number of dwellings will increase.

D)The variance of the number of dwellings will increase.

There is a gragh but I cannot draw it of course, but i think someone might remember solving that question before and can help me to understand it

You need to understand the terms mean, median, mode.

Have you seen the visual tool that Khan Academy uses to illustrate these?

If not search constructing box plots.

Now let's look at the problem:

The size of the of the plot is an unessential for answering the problem.

The size of the house is also an unessential.

At the beginning, there are let's say 5 houses on each plot.

On one plot, a family combines 2 houses. There are now 4 houses.

If on another plot, two families combine their house with another house, there will be 3 houses.

And so on..

Because there are now fewer houses on each plot, the average or mean will be smaller when they survey the plots again.

If you still don't understand,

use a tactile tool like a Lego block or penny for each house and play it out, as you read what I wrote again.