A student investigates the electrostatic charges on three objects P, Q and R. The student places object P on the insulated pan of a balance and notes the reading on the balance. The student then holds object Q a small distance above object P and notes the reading on the balance. Finally, the student holds object R the small distance above object P and notes the reading on the balance. The student’s observations are shown.
Which row gives possible charges that explain these observations?
