In experiments in which certain kinds of bacteria were placed in a generous supply of nutrients, the populations of b...

Ryan on September 29, 2019

Why is A correct? Why is C incorrect?


1 Reply

on October 2, 2019

Hello @Ryan-Mahabir,

From this experiment, the only thing we know is that some genetic mutations occurred at random. It remains possible that some other mutations occurred in sequence or in a predictable manner (not at random). Therefore, we cannot say from this information alone that all genetic mutation is random.

We need an answer choice that fixes this argument, allowing us to rightfully conclude that all genetic mutation is random.

A is the correct answer, because it removes the possibility of non-random mutations that I described above. A tells us that if some genetic mutations were random (some were), then all mutations are random. With this new information, we can say that all genetic mutation is random, because random mutations were witnessed in the experiment.

C does not have the same effect, because we still don't know if every mutation in the experiment was random. Remember, the scenario from answer choice A no longer applies. My examples above are still possible. Therefore, the "if" statement does not necessarily apply. C does not allow us to draw the given conclusion.