PLEASE HELP!!!!

Which expression is a simplified form of
[tex]3x^{2} - 4x + 5 - x^{2} + 2x - 1[/tex]
[tex]a) \: 2x^{4} - 2x^{2} + 4 \\ b) \: 2x^{4} + 6x^{2} + 4 \\ c) \: 2x^{2} - 2x + 4 \: \: \\ d) \: 4x^{2} - 2x + 4 \: \: [/tex]​