Simplify the expression.
(15 POINTS!)

[tex]6 t^{2} - 5.4 - 3.5t + 2.5x^{2} + 3t[/tex]

A. [tex]-8.5 t^{2} + 0.5t + 5.4[/tex]
B. [tex]8.5t^{2} - 0.5t + 5.4[/tex]
C. [tex]4 t^{2} - 6.5t [/tex]
D.[tex]-4 t^{2} + 6.5t [/tex]