Question 1
In activity 1, what can be said about the two spring balance readings in every case where the ring stays in equilibrium?
The right answer is the one marked above.
The two readings are equal. That is what shows the two forces on the ring to be equal in magnitude in equilibrium.
Saying the readings add up to zero is wrong — a balance never shows a negative reading. What comes to zero is the resultant, once the directions of the forces are taken into account.