When inserting an item into a binary tree,

a. the item is always inserted in the root.
b. the item is always inserted in such a way that the parent node's key is less than the item node's key.
c. the item is often placed in both the left sub-tree and the right sub-tree for ease of retrieval.
d. we must first check to determine if the tree is full.
e. we must first determine if the item's key already exists in the tree. If so, no insertion is performed.

e. we must first determine if the item's key already exists in the tree. If so, no insertion is performed.