SAT math practice question: Roots and fractional exponents

 
Try the following SAT math practice question (No Calculator) that tests your understanding of the relationship between roots and fractional exponents.

Which of the following is equivalent to $x^{\frac{4}{3}}$, where $x > 0$ ?

1. $\quad x \sqrt[3]{x}$
2. $\quad \sqrt[3]{x^4}$
3. $\quad \sqrt[4]{x^3}$

1. $\quad \textrm{I only}$
2. $\quad \textrm{II only}$
3. $\quad \textrm{I and II only}$
4. $\quad \textrm{I and III only}$