[单选题]
A 3.0-kg object moves to the right with a speed of 2.0 m/s. It collidespitfc: e6 nc1) y(ch,m:;w*hbnv gmt /in a perfectly elastic collision wiv(gyt*h:nmw;,b mh/cth a 6.0-kg object moving to the left at 1.0 m/s. What is the total kinetic energy after the collision?
A. $9.0 \; J$
B. $6.0 \; J$
C. $3.0 \; J$
D. $0 \; J$
