Which sentence needs a hyphen?
a. the television station was broadcasting live.
b. crickets are most active after dark.
c. she is a self proclaimed expert on insect behavior.
d. he wants to join the high school swim team.

the sun warms our planet, and with the moon, creates the tides. the moon orbits the earth and in turn, the earth orbits the sun. because they appear to be the same size in the sky, the sun, earth and moon work together to create eclipses. when the moon is directly in between the earth and sun

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).