Tie for Two:
B and C have only an x as the variable (not x^2)
B and D have a 9x
A and D have three different terms (once simplified)

Thread for Three:
A, B, and C can be simplified
B, C, and D are written with symbols
B, C, and D don’t have x^2

Fit for Four:
All four are expressions
All for have an x