Height of full binary tree

[Duy]

Hi everyone,

I have a problem about full binary tree like this:

Find the number of internal vertices, terminal vertices and the hight of a full binary trees have a total of 7 vertices.

I calculate the number of internal vertical is 3 and the number of terminal vertices is 4, i think it is ok. However, i am not sure about the height of this full binary tree, i try to draw and calculate the height can be 2 or 3 but i saw someone draw for a full binary tree have 7 vertices in the website http://www.maths.usyd.edu.au/u/kooc/catalan/cat13ftree.pdf, they pointed out that the height is only 3.

Can you please explain more for me about the height of a full binary tree in this case.

Thank you very much.