Asking some fixed and some random questions

Hi, we want to ask users a certain number of questions from a larger set.

 

We have the following set of questions:

1

2a

2b

3

4

5a

5b

5c

 

What’s the best way to ask 1 question for each number?

 

So questions 1, 3 and 4 are always asked. But the second question will either ask 2a or 2b and then question 5 will ask the user one of the three possible questions (5a, 5b, or 5c).

 

So there are a total of 5 questions being asked.

 

Thanks.