How would a bar magnet orient itself to this planet’s magnetic field
a.) a
b.) b
c.) c
d.)d

A bar magnet orient itself to the opposite polarity of planet’s magnetic field  

As we know that the earth acts like a very big but a weak magnet and that's why compasses point north. If we take a bar magnet and let it hang freely by the help of a string then we will see that the magnet's north pole would point to the Earth's south pole. and the magnet's south pole would point to the Earth's north pole and that is because we know that opposite poles attract each other.