Which of the following organisms is mainly found in the marine habitat?

Step 1: Analyze the question The question asks which organism lives mainly in a marine habitat, meaning the salty sea or ocean.

Step 2: Concept Habitats are grouped as:

• Marine: salt water (seas and oceans)
• Freshwater: rivers, streams, lakes, ponds
• Terrestrial: land

Step 3: Check each option

• A. Achatina is the giant African land snail. It is terrestrial.
• B. Tilapia is a very common freshwater fish found in rivers, ponds, and lakes. Some species tolerate brackish water, but it is mainly freshwater.
• C. Dog fish is a small shark (a cartilaginous fish). It lives mainly in the sea, so it is marine.
• D. Tortoise is a terrestrial reptile. Don't confuse it with the sea turtle, which is marine.

Step 4: Answer The dog fish is the organism mainly found in the marine habitat.

Exam tip: Remember that sharks and their relatives (dog fish, rays) are marine, while Tilapia, Catfish, and Mudfish are freshwater. Also remember "Achatina = land snail" and "tortoise = land." Don't be tricked by the word "fish": not every fish is marine.