NOC code has changed for me in last 10 years

Hi, my NOC code has changed thrice in past 10 years. Now there is a question which asks “No. of year of experience in past 10 years in a single occupation”

So for this question,Should my answer be just for my latest NOC only ?

You can choose the NOC in which you have max experience and for which you can get a reference letter easily.

If all three NOCs have 3+ years of experience, go with the one for which reference letter is easily available.

If you have reference letters for all 3 NOCs and all have 3+ years of experience, use the latest NOC.