@Zaw
We are in the year 2023. Don't use a book printed in 2021.

The Zone 70 should really give the answer away ...

It's a speed zone, so this speed limit doesn't end at the next junction
It ends where the zone ends ...

Please explain question 7872 from the exam:

When you leave this built up area, the maximum speed limit is 70 km/hour until the next junction.

A. Correct.
B. Incorrect.

There is a sign that shows End of Built Up Area, and below it there is a sign stating Zone 70.

I got the answer wrong. What did I miss?

Then, in the June 2021 edition, Lesson 6 has a picture of a 50 speed limit on top a End of Built Up Area sign, and the lesson states the speed limits are 70 / 70 / 90 (Flanders, Brussels, Wallonia, respectively).

I am confused and request some more explicit explanation, please.