any node n_d at level less than d-1 has two sons

it contains log(d)+1 nodes

for any node n_d in the tree with a right descendent at level d lt must have a left son

all of these

II and III

I and III

I and II

None of these

each leaf in the tree is either at level

for any node

each leaf in the tree is either at level and for any node

None of these

Complete tree

Full binary tree

Binary search tree

AVL tree

15

20

63

71