Only the second one is acceptable. (We do not share a body.)1a. There are many cells in *our body*.
1b. There are many cells in *our bodies*.
Only the second one is acceptable. (We do not share a life any more than we share a body.)2a. We do this in *our everyday life*.
2b. We do this in *our everyday lives*.
They are both right. They gave good advice.A Canadian native speaker and a reply from ASKOXFORD advised that only (1b) and (2b) are correct.
The original nutty professor, perhaps? :wink:An American professor of English advised that I should use (1a) and (2a) to 'avoid the problem of thinking that we have more than one body apiece' and likewise with 'life'.
Perhaps that person did not understand the question.A reply from Englishclub.com advised that all four are acceptable.
Some people use their in some cases instead of using he or he or she. That creates a problem of noun/verb agreement, but it does solve another problem that they think is a greater one. Otherwise, there is no reason to use their or our with a singular verb.Michael Swan's Practical English Usage says that for generalisations and rules, it is OK to use singular or plural nouns or both together with 'their/our'.