He woolly mammoth, an ancestor of the modern-day elephant, thrived millions of years ago. (1) when it first appeared, the world was very different than it is today. much of the land was frozen, which is why the mammoth needed its thick, warm coat of shaggy hair. (2) despite the cold, there was a great deal of vegetation, which the huge animals ate abundantly. mammoths were well suited for their environment. their population thrived in many of the coldest places of the world, such as alaska and siberia. around 10,000 years ago, however, something changed dramatically. (3) mammoths began to quickly disappear. today, scientists are unsure of the exact cause of this. "some speculate the climate began to change quickly, interfering with the mammoths' lifestyles and food supply," noted dr. yuri fedorsky, a russian archeologist. "others think a terrible disease might have swept across the population. still others point to the idea that people hunted the animals to extinction." some mammoths lived on isolated islands until about 4,000 years ago; however, they are all extinct today. (4)elephants, their closest ancestor, tend to live in warmer climates because they lack the thick fur of the mammoths. which sentence is not relevant to the paragraph and should be deleted? a) sentence 1 b) sentence 2 c )sentence 3 d) sentence 4