o convert an LP to standard form, which of the following statements is true? $($Please check all correct answers.$)$

A $<=$ constraint should be converted to an equality constraint by subtracting an excess variable ei from its left$-$hand side, and adding the sign restriction ei $>=0.$

For an LP with m equality constraints and n decision variables, its standard form consists of m constraints and n decision variables.

For an LP with m inequality constraints and n decision variables, its standard form consists of m constraints and $($m$+$n$)$ decision variables.

Constant terms in the objective function should be kept.

For an LP with m equality constraints and n decision variables, its standard form consists of m constraints and $($m$+$n$)$ decision variables.

All constraints must be converted to equality constraints.

A $>=$ constraint should be converted to an equality constraint by adding a slack variable si to its left$-$hand side, and adding the sign restriction si $>=0.$

All decision variables must be restricted to be nonnegative.