Which of these pose a threat to the whale population? A) whaling
B) pollution
C) global climate change
D) all of the above

Its D, all of the above.

Explanation:

Pollution can get the whales sick, global climate change can make it too hot or change the ecosystem of the whale, and whaling is straight up killing and hunting whales.

D all of the above

Explanation:

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.

it is a limiting nutrient limited by a single nutrient in the ecosystem, & the single goes very slow.