All the following empires collapsed by 550 C. E. EXCEPT Text to speech A:A. the Han Empire.
B:B. the Gupta Empire.
C:C. the Roman Empire.
D:D. the Sassinian Empire.

C. The Roman Empire which didn't even exist for another 520-ish years.

Explanation:

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.