SAT World History Practice Question

What was the primary reason Russia ended its involvement in World War I?

1. A.The population devastation wrought by massive casualties
2. B.The diplomatic agreement signed with Germany for territory in East Europe
3. C.The adversarial nature of the relationship with the French and British allies
4. D.The internal political dissent against the czarist government
5. E.The severe economic strain placed on the country by its war efforts