That is the estimate that most doctors practice to measure due to date, and it's based on the first day of your last menstrual phase. It technically involves almost two weeks where the woman was not pregnant. Gestational age is the age of the productivity from the last common menstrual phase.
I would say a because he ran too much but that would be just me I think he hurt his knee from running too much more exercise but probably just aggravate his condition I could be wrong but this is what I think