Fill in the blanks. The chemical effect of an electric current on a potato causes a blue-green spot to appear near the
terminal of the battery

Correct question is;

Fill in the blanks: The chemical effect of an electric current on a Potato causes a blue green spot to appear near the terminal of the battery

Positive

Explanation:

For example, when we want to pass current through potato, we usually connect the ends of a battery by using copper wire with potato and inserting it inside. Now, the electrons from the negative terminal of the battery through the copper wire will reach inside the potato where they undergo electrolysis of part of the copper wire inside the potato in the presence of starch or potato juice.

This process means that the electrons released increase the negative particles and when these negative particles reach the other end terminal, it reacts with the copper inside the potato to form a complex form which is greenish blue in colour.

This greenish blue colour is an evidence of the presence of the positive terminal.

the first one is d and the second a