People all over the world react similarly when they are reunited with loved ones. for example, if you watch people greeting each other at family reunions, they tend to have the same joyful expressions on their faces, no matter what country they come from. this similarity can be attributed to: our family upbringing being so similar. our cultures being so similar. our shared human genome. random errors in gene replication.

Our shared human genome. Let's look at the options and see what makes sense and what doesn't. A. Our family upbringing being so similar. * Nope. We're talking completely different cultures and as such completely different upbringing. So this conclusion isn't reasonable at all. So this is a bad choice. B. Our cultures being so similar. * Nope. Different cultures, different languages, different ways of looking at things. So an unreasonable conclusion and a bad choice. C. Our shared human genome. * We do share a common genome. So this is the best choice so far. Let's see if there's something better as a later choice. D. Random errors in gene replication. * Random errors would imply different responses. So this conclusion doesn't make sense and is therefore a bad choice. So the only reasonable choice is the choice indicating something that we share in common with many different cultures. That being our genome. So option "C" is the best choice.