The answer to this question is A. Jet streams
Jet streams are located near the altitude of the upper troposphere. It's a movement of wind that travels from one side of the planet hemisphere to another. The movement of jet streams will bring up different temperature of air which could influence the weather that exist in certain regions.
A. Urban II
These incursions prompted the emperor of Byzantium, Alexius I Comnenus to send a delegation to Piacenza, Italy, asking Pope Urban II in March 1095 for help against the Turks. On November 27, 1095, in Clermont, France, Pope Urban II called for a crusade to help the Byzantines and to free the city of Jerusalem.
Since then the Great Wall was built, rebuilt to protect the northern borders of the Chinese Empire from the Hun's and Mongolian attacks during the rule of successive dynasties.
This question is a little ambiguous as it doesn't give reference to what 'favourable' is but I've attached a diagram that depicts the different types of climate in Brazil to help.
(This is more of a geography question than history)
