Answer
No, this is not a strong acid.
Work Step by Step
1. If this monoprotic acid is strong: $[H^+] =0.0642$, because the acid would completely hydrolyse.
2. Calculate the concentration of $H^+$ in this solution:
$$[H^+] = 10^{-pH} = 10^{-3.86} = 1.4 \times 10^{-4} \space M$$
3. Since the concentration is less than 0.0642, this is definitely a weak acid.
