1. **State the problem:** Simplify the expression $$7^1 y^3 y^3 y^3$$. 2. **Recall the rules:** When multiplying powers with the same base, add the exponents: $$a^m \times a^n = a^{m+n}$$. 3. **Apply the rule to the variable part:** $$y^3 \times y^3 \times y^3 = y^{3+3+3} = y^9$$ 4. **Rewrite the expression:** $$7^1 y^9 = 7 y^9$$ 5. **Final simplified form:** $$7 y^9$$ Therefore, the correct answer is **7y^9**.