Which choice does not contain a run-on sentence? (points : 3)
the big dipper makes a good reference point these stars are almost always visible in the northern hemisphere.
because the big dipper is almost always visible in the northern hemisphere, these stars make a good reference point.
the big dipper is almost always visible, these stars make a good reference point in the northern hemisphere.
the big dipper is almost always visible in the northern hemisphere these stars make a good reference point.