Which equation describes a linear function

plsss me

B

Step-by-step explanation: for number 3, a linear function is anything that is raised to the first power so in this case it would be B.

The missing justification in the proof is
B) Substitution property of equality

The expression for sin² x and cos² x is substituted to the other side of the equation. Since sin x = a/c, then sin² x = a²/c². Similarly, since cos x = b/c, then cos² x = b²/c². Adding to two results to the third statement.