|Question 2Verbal

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Text
When minor planets are discovered, each is given a unique identification number, and some may be given a unique name, as in the case of 1083 Salvia, which was named after the plant genus that includes sages. Under current astronomical conventions, it is        for the discoverers to name their discoveries, but they are not required to do so; whether to assign a minor planet a name is entirely the choice of whoever discovers it.
Which choice completes the text with the most logical and precise word or phrase?
permissible
A
infeasible
B
selective
C
mandatory
D