Two blocks $A$ and $B$ of mass $2 m$ and $m$ respectively are connected by a massless spring of spring constant $K.$ This system lies over a smooth horizontal surface. At $t=0$ the block A has velocity $u$ towards right as shown while the speed of block $B$ is zero, and the length of spring is equal to its natural length at that instant. In each situation of column-I, certain statements are given and corresponding results are given in column II. Match the statements in column I corresponding to results in column-II.

	Column-I		Column-II
P	The velocity of block A	1	can never be zero
Q	The velocity of block B	2	may be zero at certain instants of time
R	The kinetic energy of system of two blocks	3	is minimum at maximum compression of spring
S	The potential energy of spring	4	is maximum at maximum extension of spring