Which one of the following Acids is most likely to hurt you? Acid A: 1.0 M; Acid B: 0.0001M

Acid A, assuming the two acids have the same pH. The M stands for molarity which is how concentrated a substance is (basically the higher the molarity the more concentrated the acid is). However, pH refers to how acidic a substance is. If the two acids have different levels of acidity, the answer may be different.