Some Types of Fish Have Specialized Cells Called Electrocytes That

Some types of fish have specialized cells called electrocytes that generate an electric field around their body with which they communicate with other individuals of the same species and can stun prey. Researchers hypothesized that electrocytes produce the electric field in response to blood levels of a hormone called ACTH, and that it was a positive relationship (higher levels of hormone results in a stronger electric field) . Which of the experiments below is the MOST direct test of this hypothesis?

A) While measuring the strength of a fish's electric field, inject it with ACTH.
B) Take a blood sample from a fish that is producing a strong electric field; inject the blood into a second fish and measure its electric field strength.
C) Take a blood sample from a fish that is producing a strong electric field and measure the ACTH levels.
D) Remove the pituitary gland, which secretes ACTH, from a fish and measure its electric field strength.
E) While measuring the strength of a fish's electric field, inject it with a saline solution.