Type missmatch cannot convert from Fragment to fragment

I'm getting this error at the moment:

"type missmatch cannot convert from FragmentA to fragment". 

Under each If statement

    if(arg0==0)
    {
        fragment=new FragmentA(); 
    }

if(arg0==0)
    {
        fragment=new FragmentB(); 
    }

if(arg0==0)
    {
        fragment=new FragmentC(); 
    }

So I'm wondering if it's something to do with my import files? As I keep having trouble with those. I'll list the Import files and then the relevant code. Could be either the method or the imports not to sure which.

Ok so here is the full code:

    import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBar.Tab;
import android.support.v7.app.ActionBar.TabListener;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.Toast;

public class Main_activity extends ActionBarActivity implements TabListener {



    public static final String PREFS_NAME = "MyPreferncesfile";

    ViewPager viewPager; 
    ActionBar actionBar; 
    @Override
    public void onCreate(Bundle arg0) {
        super.onCreate(arg0);
        setContentView(R.layout.activity_main);

        viewPager=(ViewPager) findViewById(R.id.pager);
        actionBar=getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        ActionBar.Tab tab1=actionBar.newTab();
        tab1.setText("Tab 1");
        tab1.setTabListener(this); 

        ActionBar.Tab tab2=actionBar.newTab();
        tab2.setText("Tab 2");
        tab2.setTabListener(this); 

        ActionBar.Tab tab3=actionBar.newTab();
        tab3.setText("Tab 3");
        tab3.setTabListener(this); 

        actionBar.addTab(tab1);
        actionBar.addTab(tab2);
        actionBar.addTab(tab3);
     }
    public void onTabReselected1(Tab tab, FragmentTransaction ft) {

        Log.d("VIVZ", "onTabReselected at "+" position "+tab.getPosition()+" name "+tab.getText());


    }

    public void onTabSelected1(Tab tab, FragmentTransaction ft) {
        Log.d("VIVZ", "onTabSelected at "+" position "+tab.getPosition()+" name "+tab.getText());

    }

    public void onTabUnselected1(Tab tab, FragmentTransaction ft) {
        Log.d("VIVZ", "onTabUnselected at "+" position "+tab.getPosition()+" name "+tab.getText());

    }



    class MyAdapter extends FragmentPagerAdapter 
    {

        public MyAdapter(FragmentManager fm) {
            super(fm);
            // TODO Auto-generated constructor stub
        }

    public Fragment getItem(int arg0) {
        Fragment fragment=null; 
        if(arg0==0)
        {
            fragment=new FragmentA(); 
        }
        if(arg0==1)
        {
            fragment=new FragmentB(); 
        }
        if(arg0==2) 
        {
            fragment=new FragmentA(); 
        }
        return fragment;
    }


        @Override
        public int getCount() {
            return 3;
        } 
    }