选择题
2010 AMC 8 Problem 25: Climbing Six Stairs
Everyday at school, Jo climbs a flight of 6 stairs. Jo can take the stairs 1, 2, or 3 at a time. For example, Jo could climb 3, then 1, then 2. In how many ways can Jo climb the stairs?
A.
13
B.
18
C.
20
D.
22
E.
24