In the following question, a sentence is given with four words highlighted in bold as (A), (B), (C), and (D). These words may not be in their correct positions. Select the option that gives the correct pair of words that should be interchanged to render the sentence grammatically correct and meaningful.

Acoustic (A) organisms (B) are frequently tracked using aquatic (C) transmitters (D).

The correct option is A-C.

Explanation:
The given sentence is: "Acoustic (A) organisms (B) are frequently tracked using aquatic (C) transmitters (D)."

Let's analyze the highlighted words and their context:
1. Organisms (B) living in water are referred to as aquatic organisms. Therefore, word (C) "aquatic" should modify "organisms".
2. Devices that emit sound pulses to track movement in water are known as acoustic transmitters. Therefore, word (A) "Acoustic" should modify "transmitters".

Interchanging words (A) and (C) renders the sentence logically sound and grammatically correct:

"Aquatic (A) organisms (B) are frequently tracked using acoustic (C) transmitters (D)."

Hence, the correct pair of words to interchange is A-C.