Final answer:
The correct expression to convert 1.338 x 10¹ km³ to cubic meters is 1.338 x 10¹ km³ x 10¹ which results in 1.338 x 10¹¹ m³, so the answer is option D.
Step-by-step explanation:
The question asks about converting the volume of the world's oceans from cubic kilometers to cubic meters. To convert cubic kilometers to cubic meters, we multiply the value by 109 (since 1 km3 = 109 m3). Therefore, to find out how many cubic meters are in 1.338 x 109 km3, the correct expression would be 1.338 x 109 km3 x 109 (for the cubic meters per cubic kilometer), which yields 1.338 x 1018 m3. So the correct option is D.