GROUPING #$3$ At a given organization, the EdvisitFact table has $750$ rows of data. Exactly $250$ of those rows store a NULL value in a column named Observation Started instant. What value would a query of "SELECT COUNT Observation Startedinstant$)$ FROM EdVisitFact' return? SELECT ONE OF THE FOLLOWING $(2$ PTS$)$ A$.$ O $$ B$.250$ C$.500$ D$.250$