The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
The most valid counter-argument to the description of the Mongols by the Russian duke was that the Mongols were interested only in plunder and treasure but not in controlling the Russian territory.
As we know by reading this part of history, the Mongols were terrible warriors that showed no mercy. They were fierce fighters that indeed were interested in destroying and plunder. And more than conquering and establish a form of government to rule a territory, by the way, they attacked and proceeded, it seemed that they were more interested in becoming wealthy.
Duct Tape.
Remember the Dept of Homeland Security warning to purchase duct tape and plastic to help against biological or chemical attacks. And yes, NASA does send up duct tape with every flight. It was useful in the famous troubled Apollo 13 mission, and was credited in part with saving the lives of those astronauts.
They were conquered by the Spanish.