The northern european plain stretches from the atlantic ocean to
a. appalachian mountains
c. eurasian peninsula
b. ural mountains
d. pacific ocean

Appalachian Mountains are in North America, so it can't be the correct answer.

Also I don't know of anything called "Eurasian Peninsula" - also false.

They don't reach the Pacific - that would mean they cover all of Asia!

So the correct answer is: b. Ural Mountains

The investiture controversy began as a power struggle between pope gregory vii (1072–85) and henry iv, holy roman emperor (1056–1106).[2] a brief but significant struggle over investiture also occurred between henry i of england and pope paschal ii in the years 1103 to 1107, and the issue played a minor role in the struggles between church and state in france, as well.by undercutting the imperial power established by the salian emperors, the controversy led to nearly 50 years of civil war in germany, and the triumph of the great dukes and abbots. imperial power was finally re-established under the hohenstaufen dynasty. historian norman cantor: