The diagram shows the electric field lines around two charges.

based on the field lines, what is the best description of the charges?

they are negative, and they repel.
the left is negative and the right is positive, so they attract.
the left is positive and the right is negative, so they attract.
they are positive, and they repel.

The correct answer is

They are positive, and they repel.

In fact, we know that for a positive charge, the lines of the electric field generated by the charge point away from the charge, as in this figure. Therefore, both charges are positive. Moreover, we also know that like charges repel each other, while opposite charges attract each other: in this case, since we have two charges of same sign, they repel each other.

d. platinum would have the greatest temperature increase because it has the lowest specific heat.