Why the presence of mountains can increase the amount of rainfall?

"Mountains pose a significant obstacle to stable air flow. As air approaches the mountain it is forced upwards. At higher altitudes, the temperatures drop, condensing water vapor. This process results in the formation of clouds. Mountains may also restrict or slow down air flow. This restriction may also result in lifting air to high altitudes and creating clouds prior to the air reaching the slopes of the mountain." - https://sciencing.com/do-mountains-affect-precipitation-8691099.html just put this in your own words. 

The answer is a but it also might be 7 so

Ithink its deforestation.