Which of the following best describes magnetic fields? a. magnetic fields need a conductor. b. magnetic fields are always found in insulators. c. magnetic fields have north and south magnetic poles. d. magnetic fields must have only positive charges.

C

Explanation:

Because the north and the south pole are like the earth if they didn't attracted  we would all die.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.