17.A mass block m₁ slides along a frictionless table with a speed v₁. In front of it is a mass block m₂ moving at speed v₂ ＜ v₁. A massless spring of spring constant k is attached to the backside of m₂. They collide with each other and separate after the impact. Which statements are correct?

(A) The shortest distance between these two blocks is
(B) The maximum compression of the spring is 
(C) The kinetic energy of the whole system is conserved during the collision process.
(D) The velocity of the center of mass of the system keeps unaltered during the collision process.
(E) The absolute value of the relative velocity between these two blocks is always v₁ - v₂.