Final answer:
Acid B with pKa=-1 is the strongest acid among the four options, with the acids ranked from strongest to weakest as B, D, C, A. Option B is correct.
Step-by-step explanation:
The strongest acid is determined by the value of its acid-ionization constant (Ka) or its negative logarithm (pKa). A smaller pKa value indicates a stronger acid. Comparing the given values, Acid B with pKa=-1 is the strongest because a negative pKa value signifies an acid stronger than hydronium ion (H3O+), thus it has a larger Ka.
The ranking of the acids from strongest to weakest based on the provided values is Acid B (pKa=-1), Acid D (pKa=0.5), Acid C (Ka=2), and Acid A (Ka=5).
For Acid B and Acid D, the given pKa values were directly used to assess strength; whereas for Acid C and Acid A, a lower Ka value indicates a weaker acid. To further clarify, a large Ka translates to a small pKa, and hence a more potent acid.
The strongest acid is the one with the highest value of acid ionization constant, Ka. In this case, the acid with Ka=5 is the strongest acid because it has the highest value compared to the other acids.