Singular or plural noun after "their" when subject is "those" (as in "those who were") Details follow

I'm helping a nephew edit a paper and while he says it isn't essential that it be grammatically perfect...😲 well. I don't know have to explain. You are my people. So without further ado, which option is correct:

A. This means that those who were indoctrinated at a young age may be hesitant to discuss their background.

B. This means that those who were indoctrinated at a young age may be hesitant to discuss their backgrounds.

I know the entire structure is awkward, and has to GO. But I became fixated on this issue, and would love the answer--more for me than for him at this point. Ha! Thank you in advance.

Solution 1:

I would suggest B. The singular they is still not accepted by all purists, and for A to be grammatical, you need to accept the singular they.

A. This means that those who were indoctrinated at a young age may be hesitant to discuss their background.

For this to be grammatical, you need to accept the singular "they". If you say "their background", you assume that there is only one background, which means that "their" can only reference one person. Consider the phrase "Everybody has their ..." The word "everybody" is singular, so using the traditionally accepted grammar, you could say "everybody has his" or "everybody has his or her", but not "everybody has their". Ngrams shows that people generally did not use their in this phrase before around 1960.

B. This means that those who were indoctrinated at a young age may be hesitant to discuss their backgrounds.

This is grammatically sound whether or not you accept the singular they, so if you are writing an assignment for a teacher whose views on singular they you don't know, it's the better choice.