[单选题]
Two objects collide and bounfvf k+l.ua(9vkazb2q:sic /dv* )1 qoce off xr 6xf nsf4ipe-f3-b; each other. Linear momentum
A. is definitely conserved.
B. is definitely not conserved.
C. is conserved only if the collision is elastic.
D. is conserved only if the environment is frictionless.
