Which of the following whale species has a long external tusk?

a.
sperm whale

b.
narwhal

c.
beluga whale

d.
bowhead whale

e.
blue whale

Answer: B.  narwhal

The narwhal is the whale species that has a long external tusk protruding from a canine tooth. However, the function of this strange structure has remain a mystery for a long time, recent drone footage may have found the answer.  

Although it is believed that this 3 meter tooth may play an important role in mating, another function for it may be in hunting fish. In the footage, the individual uses it to hit the fish and thus stun it.

Furthermore, another function may also be echolocation, through which marine species, especially dolphins, use sound waves to "see" underwater.

meiosis is the correct answer