In a System of M Simultaneous Equations,at Least M-1 Variables

Multiple Choice

In a system of M simultaneous equations,at least M-1 variables must be excluded from each equation for the equation to be identified.What does it mean if the equation is not identified?

A) unique coefficient estimates for each variable cannot be identified using least squares
B) the economic value of the predicted value cannot be identified
C) the economic relationships are unclear and the equation should be dropped form the system
D) the exogenous variables have been incorrectly identified