In a multiple-choice test, an examinee either knows the correct answer with probability p, or guesses with probability 1 - p. The probability of answering a question correctly is , if he or she merely guesses. If the examinee answers a question correctly, the probability that he or she really knows the answer is

• A. \(\frac{{{\rm{mp}}}}{{1 + {\rm{mp}}}}\)
• B. \(\frac{{{\rm{mp}}}}{{1 + \left( {{\rm{m}} - 1} \right){\rm{p}}}}\)
• C. \(\frac{{\left( {{\rm{m}} - 1} \right)}}{{1 + \left( {{\rm{m}} - 1} \right){\rm{p}}}}\)
• D. \(\frac{{\left( {{\rm{m}} - 1} \right){\rm{p}}}}{{1 + {\rm{mp}}}}\)