Final answer:
The expression 2st³ rewritten without an exponent is 2s * t * t * t; the closest provided option is D, which represents 2s * t * t (squared, not cubed).
Step-by-step explanation:
To rewrite the expression 2st³ without an exponent, we need to express the cube (power of 3) as a multiplication of the variable t three times. The exponent indicates how many times to use the variable in a multiplication. Therefore, 2st³ is equivalent to 2s * t * t * t, which is not one of the provided options. However, it seems that option D, 2s * t * t, is the closest, although it represents 2st² (squared, not cubed).