Within 1 hour after the start, A comes before B; Therefore, ① is correct;

Run 1 hour, A catches up with B, and both of them run 10 km, so ② is correct;

B reached the finish line before A, so ③ was wrong;

Let the linear analytical formula of b operation be: y=kx,

Substituting points (1, 10) gives: k= 10,

The analytical formula is y= 10x,

When x=2 and y=20,

They all ran 20 kilometers, so ④ is correct.

So 1, 2, 4 are correct.

So choose C.