In this question, we are asked to identify the pair that is not correctly matched in terms of the organ/part that assists in locomotion.

Option 1 states that Euglena has a flagellum for locomotion. This is correct, as Euglena is a unicellular organism that moves by using a whip-like tail called a flagellum.

Option 2 states that Paramecium uses cilia for locomotion. This is also correct, as Paramecium is another unicellular organism that moves by beating hair-like structures called cilia.

Option 3 states that Nereis has pseudopodia for locomotion. This is not correct. Nereis is a polychaete worm, and it uses parapodia, not pseudopodia, for locomotion. Parapodia are fleshy, paddle-like appendages that help the worm crawl or swim.

Option 4 states that Starfish uses tubefeet for locomotion. This is correct, as starfish have numerous tube-like structures called tube feet that they use for crawling and gripping surfaces.

Therefore, the correct answer is option 3, as the pair Nereis and pseudopodia is not correctly matched. Alert - correct answer should be