The correct answer is: C. A is true, but R is false.
Formic acid is a stronger acid than acetic acid. This is because formic acid has a higher pKa value than acetic acid. The pKa value is a measure of how easily an acid dissociates in water. A higher pKa value means that the acid is less likely to dissociate, and therefore a stronger acid.
The reason given in the question is that formic acid is an organic acid. However, this is not a correct explanation for why formic acid is a stronger acid than acetic acid. There are many organic acids that are weaker than acetic acid, such as propionic acid and butyric acid.
The correct explanation for why formic acid is a stronger acid than acetic acid is that formic acid has a smaller molecular size. The smaller the molecular size, the more easily the acid can dissociate in water. This is because the smaller molecules can more easily penetrate the water molecules and interact with the hydrogen ions.
In conclusion, formic acid is a stronger acid than acetic acid because it has a higher pKa value. The reason given in the question is not a correct explanation for why formic acid is a stronger acid than acetic acid. The correct explanation is that formic acid has a smaller molecular size.