Target question: is m > k?
Statement 1: 3m > 3k
Divide both sides of the equation by 3;
$$We\ have\ m>k$$
This provides an answer to the answer target (i.e Yes, m>k). Hence, statement 1 is SUFFICIENT.

Statement 2: 2m > 2k
Divide both sides of the equation by 2;
$$We\ have\ m>k$$
This provides an answer to the answer target (i.e Yes, m>k). Hence, statement 2 is also SUFFICIENT.

Since each statement alone is sufficient, option D is, therefore, the correct answer.