Which of the following typical adaptations of marine animals is not found in sea otters?
a. streamlined body
b. webbed hands and feet
c. body covered in thick fur
d. breathing apparatus on the top of the head

Unlike fully aquatic marine mammals, or Cetacea, sea otters are bi-terrestrial and are capable of living on both land and in the water. Like all marine mammals, otters have webbing between their toes with acts like a flipper as well as a streamlined body to enable them to move quickly through the water. The only adaption that is not applicable to otters is d. breathing apparatus on the top of the head. Only marine mammals such as whales, dolphins, and porpoi have a blow hole on their dorsal side of their body. Another difference from Cetacea is an otter's thick fur. I believe the ratio for pelt density is one million lock of fur per square inch. Otter fur is also much longer compared to that of other marine mammals like pennipeds. Their long fur makes otters especially susceptible to oil and oilspills resulting from underwater oil mining accidents.

That would be a working theory.