A horizontal force F is applied on a rod inserted between two identical blocks A and B placed over a rough surface as shown.Force F is gradually increased then which of the block will move first.

Question

$\begin{array}{1 1} (a) block A \\(b) block B \\ (c) \text{Both will move simultaneously } \\ \text{d) will depend on friction between block and ground.}\end{array}$