The answer is D- the casualty rate of their own army was high.
Russia was also in a civil war, causing the death of many soldiers <span />
Cheng Ho. He had a large fleet of ships that sailed around the various oceans in the Orient, as well as the Indian Ocean.
Puerto Rico,Guam,and The Philippines
Long distance communication depended on the memory of a man, long-term memory was needed to teach children, and construction was more slow paced.