if we analyse a binary tree there is a connection between nodes of degree 2 and leaves
e.g
1 node of degree 2 => 2 leaves
2 nodes of degree 2 => 3 leaves
in general n nodes of degree 2 => n+1 leaves
NOTE:here degree is considered as out degree only.
so for above question there are 10 nodes of degree 2=>10+1=11 leaves
option (B)