a. Intent intent = new Intent(this,new Activity2());
startActivity(intent);
b. Intent intent = new Intent(new Activity2());
startActivity(intent);
c. Intent intent = new Intent (Activity1.class,Activity2.class);
startActivity(intent);
d. Intent intent = new Intent(this,Activity2.class);
startActivity(intent);
d. Intent intent = new Intent(this,Activity2.class);
startActivity(intent);