The notice said that the meeting would begin precisely at 9.00 a.m.

Answer: Option C

Concisely : in a way that is brief but comprehensive.
Approximately : used to show that something is almost, but not completely, accurate or exact; roughly.
Exactly : used to emphasize the accuracy of a figure or description.
Inaccurately : in an incorrect or inexact manner.
Precisely : in exact terms; without vagueness.

Synonym of Precisely is Exactly