1998 chevy cavalier act like going to start but wont start?is it the fuel...

...pump? replaced relay,what is it? If it is the fuel pump,which one do i get,do i need to replace the fuel line to?could it be the fuel filter?when you turn key car acts like its going to start but does not.
what could it be

wel heres what id do first remove fuel line up on motor is there fuel there its working you can also crank motor over once or twice to see if fuel sprays out line when you crank over got to have fuel and spark so when was last time to replace plugs or when was last time you added any fuel treatment to keep fuel lines clean