What happens to compass needles when a copper rod is placed at a 90 degree angle in the midst of them and electric current is flowing through the rod?

we can answer this one very quickly.   from the law of conservation of energy, we know that "energy can't be created or destroyed.".

so that only leaves us one way to complete the sentence in this question:

"one form of energy can be transformed into another type of energy. "   (b)

b and c are both true.

their final velocity   is 0.48 m/s.

we can use conservation of momentum to calculate the magnitude of the final velocity.

momentum before collision is equal to the momentum after collision

m1v1+m2v2=(m1+m2)v

here, v is final velocity , assuming right side velocity as positive, and left side velocity as negative.

14*(-1.1)+18*(0)=(14+18)v

v=-0.48 m/s

here, negative sign indicates that they both   will move in left direction.