As many as 30 thousand become entangled in lost or discarded fishing nets or cargo straps each year.

As many as 30 thousand fur seals become entangled in lost or discarded fishing nets or cargo straps each year.

Explanation:

Human activities cause many damages to marine mammals in general. One of these activities is fishery. The nests are intercepting the migratory routes of animals or are floating free in the sea after being discarded. They are extremely strong, so whenever animals get stuck on them, they might carry them for months or years, affecting their diving, foraging, feeding, and reproductive behavior. These nets might hurt the animals´ skin, producing a wound that will probably get infected.

A few years ago, at least 50,000 northern fur seals died per year after getting stuck in fishing nets. The populations of these animals decreased sharply, affecting their reproductive and growth rates. In the present, due to the decrease in their population size, the number of dead animals is around 30,000 per year. This reduction in death is only because there are much fewer animals every year.

b is the best answer for this question.

amber has allowed scientists to study dna that has been preserved over millions of years.