Final answer:
The diameter of Earth in decimeters is 1.3 x 10^8 dm.
Step-by-step explanation:
To convert from kilometers to decimeters, we need to know the conversion factor between the two. There are 10 decimeters in 1 meter, and 1000 meters in 1 kilometer. So, there are 10 x 1000 = 10,000 decimeters in 1 kilometer. Therefore, we can calculate the diameter of Earth in decimeters by multiplying the given diameter in kilometers by the conversion factor:
1.3 x 10^4 km x 10,000 dm/km = 1.3 x 10^4 x 10,000 dm = 1.3 x 10^8 dm
So, the diameter of Earth expressed in decimeters is 1.3 x 10^8 dm, which corresponds to option D.