1) A Binary Tree can have
1. Can have 2 children
2. Can have 1 children
3. Can have 0 children
4. All

Explanation: Binary tree can have at most 2 children.

2) Height of Height of a binary tree is
1. MAX( Height of left Subtree, Height of right subtree)+1
2. MAX( Height of left Subtree, Height of right subtree)
3. MAX( Height of left Subtree, Height of right subtree)-1
4. None

3) Postfix expression for (A+B) *(C+D) is
1. A B C * + D +
2. A B + C D + *
3. ABCD++*
4. None

In postfix form two operands come together then operator. For example, in A+B, A and B are two operands and + is one operator and A+B is in infix form. Hence, in postfix of A+B will be AB+.
Let’s consider the question above
(A+B) *(C+D)//this expression is in infix form
First get A and B operand together then operator +. Similarly, for C and D
(AB+) * (CD+)
now consider AB+ and CD+ as two operands. Take them together then * operator.
(AB+) (CD+) *
Remove brackets.
AB+CD+*
So, AB+CD+* is the postfix expression of (A+B) *(C+D) infix expression.

4) True statements about AVL tree are
1. It is a binary search tree.
2. Left node and right node differs in height by at most 1 unit
3. Worst case time complexity is O(log2n)
4. Worst case time complexity is O(n)

A side note: AVL tree is a self balancing binary tree and named after inventors Adelson-Velsky and Landis …wikipedia..

5)Match the following for binary tree traversal
1. 1 → A, 2 → B,  3 → C
2. 1 → C, 2 → B,  3 → A
3. 1 → A, 2 → C,  3 → B
4. 1 → B, 2 → A,  3 → C