Abag contains four red marbles and four blue marbles. you randomly pick a marble without returning the marbles to the bag. both marbles are red.

I suppose this is in reference to the chance?

The chance of choosing either red or blue marbles is 50/50 considering that there if four of each type in the bag.

The person chose 2 times, and each time go a red marble. The chance of choosing either is still 50% and they are both equally likely to get chosen. 

Technically speaking, histograms are another version of bar charts, if you need to work one out then skim through google hope-o that -o!