Who were those toolmakers

A．It shows that modem humans lived in the Arctic more than 3,000 years ago.
B．It shows that Neanderthals lived in the Arctic more than 3,000 years ago.
C．It shows the oldest documented evidence for human presence at such high latitude.
D．It shows human could use tools 30,000 years ago.

A．Because it was the longest tusk ever found.
B．Because there were signs left by human' s tools on it.
C．Because there were grooves on it.
D．Because there are not any mammoth tusk all over the world.