In the figure shown, upper block of mass $m$ is on a rough lower block of mass $M$ on a smooth horizontal surface. A horizontal force $F$ is applied to the lower block.

STATEMENT-1: The upper block is always relatively at rest w.r.t. the lower block, whatever be the magnitude of force.

STATEMENT-2: Maximum acceleration of upper block is $\mu g$, where $\mu$ is the coefficient of friction between upper and lower block.