Q. Which of the following grammar rules violate the requirements of an operator grammar ? P, Q, R are nonterminals, and r, s, t are terminals.
1. P → Q R
2. P → Q s R
3. P → ε
4. P → Q t R r

• (A) 1 only
• (B) 1 and 3 only
• (C) 2 and 3 only
• (D) 3 and 4 only