Let OPT$($I$)$ denote the minimum $($optimal$)$ number of bins for an instance I of the standard bin packing problem. For an approximation algorithm $($heuristic$),$ a worst$-$case performance ratio of $2$ means that...

Question $4$ Select one or more:

a$.$

there exist better approximation algorithms that have a better $($smaller$)$ performance ratio.

b$.$

for any instance I, the number of bins used by the resulting packing never exceeds $2*$ OPT$($I$).$

c$.$

for any instance I, the number of bins used by the resulting packing is larger than or equal to $2*$ OPT$($I$).$

d$.$

on average, the number of bins used by the resulting packing equals $2*$ OPT$($I$).$