The answer is “Overreacts to an antigen”
Well I don't know much but I do know that they are different because unicellular can self produce which means they can reproduce without someone else but multicelluar needs someone else to reproduce
The 3rd one because when you burn coal it releases toxic"air".
A. Natural Selection. This is because the weeds that are not resistant to it die out before they can reproduce, but the resistant ones grow to maturity and then reproduce, passing down the resistance gene. Over time, the resistance gene would become a normal thing in weeds, while the non-resistant gene would not exist anyone, since the gene could not be passed on.