I solve this one:

Last thursday, during the lesson Rubén asked me something as
“How many pair bases do we find per helical turn in DNA?

He was confused because not all DNA drawings have the same proportions so the question could be simplified as “Which one of these two images is more realistic?

I answered Rubén´s question doubting a bit with a number between 3 and 4, and I am sorry but I was mistaken, may be I was thinking in the 3.4 Å that is the average distance between base pairs, or may be I was mistaken because each DNA turn is also 3.4 but in this case nm, anyway…

The correct answer to the question:
How may base pairs are in a “normal” DNA molecule per complete turn?
It is 10 bases per turn.

You have the whole data to answer this, for example here.

Thanks for questioning, that make us improve.