Multiple choice

Cartilaginous fishes accumulate ____ in the blood instead of excreting it as a waste.

  1. oxygen

  2. nitrogen

  3. urea

  4. ammonia

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cartilaginous fish, such as sharks, retain high concentrations of urea in their blood. This helps them maintain osmotic balance with the surrounding seawater.