both versus two
Hello, everyone!
The task is to put either “both” or “two”. I’ve chosen “both” but the key says I am wrong.
Could you please explain why I should have chosen “two”?
“According to research, the friends, employees and role models that we choose depends on their facial symmetry. That is, on how alike the (8) _??__ sides of their face are. Scientists say that human beings have developed this characteristic in order to make sure that the healthiest and smartest humans survive.”
Thank you!