Which number contains a sentence error?
1.Peregrine falcons are great fliers, and they help keep the pigeon population down in some cities.
2.Peregrine falcons are great fliers, they help keep the pigeon population down in some cities.
3.Peregrine falcons are great fliers; they help keep the pigeon population down in some cities.
4.Peregrine falcons are great fliers. They help keep the pigeon population down in some cities.