Answer
c)
Work Step by Step
It is less than 2N. After all, the net force on the overall system (the two blocks) is 2N. This gives them a constant acceleration. However, recall that $F_{12} = \frac{m_2}{m_1+ m_2} \times F$ Thus, the force on block two, the three kilogram block, will be less than the overall net force.
