One
They have one point in common.
One
One
They can have only one point in common.
maybe
No, they only have the one common endpoint in common.
One
If the two lines are actually "on top of each other", they can have infinitely many points in common. If they are parallel, they have no points in common. If they are perpendicular, they have one point in common.
the parallel lines never intercept so they do not have any common points.
a safety is worth 2 points for the opposite team.
opposite rays have common end points
opposite angles