what does the parameter additive do?

In the set extcommunity rt 123:750 additive command, what does the parameter additive do?

A.
Replaces the existing set of route targets with a new set.

B.
Adds the new route target to the existing route target list but does not replace any existing route targets.

C.
Adds the new route target to the existing route target list and replaces the most current route target.

D.
Adds the new route target to the existing route target list and replaces the least current route target.