Which of these helps explain why migration to North America was attrac

Which of these helps explain why migration to North America was attractive to Siberian hunter-gatherers?

A) North America was home to many large mammals.
B) It was much warmer in North America than in Asia.
C) Siberian hunter-gatherers were often attacked by more aggressive Asian peoples.
D) The population of Asia had grown too large to be supported by available resources.

ANSWER
Answer: A