D. The reason for the fall of the Maya civilization is still unknown. There are many different theories attempting to explain the cause of the Classic Maya collapse and the abandonment of Maya cities in the southern Maya lowlands of Mesoamerica between the 8th and 9th centuries: climate change, drought, deforestation, etc. but although the drought is the leading theory at the moment the truth is yet unknown.
Basically North African and Middle Eastern cultures have very similar traditional clothing styles, food, architecture, beliefs and art.
This is caused by two main factors: common environment and common rulers.
Both North Africa and the Middle East are hot, dry and deserty. Dominated by the Arabian-Syrian/Sahara Deserts, both cultures were greatly influenced by their harsh environment that necessitated certain adaptions (most notably clothing and certain foods, pork for example generally rots easily in the desert and becomes dangerous to eat).
There is also the issue of their common religion/rulers. A large portion of their joint history has been spent serving under one ruler or another (Rome, Abbassids, Ottomans, etc.) They also share a common religion, greatly influencing eachother.
The answer to the question presented above would be letter b. amount of dissolved gases. The increased pressure increases the body's amount of dissolved gases. This change to air pressure greatly affects the human body and these changes can happen when going into the depths of the ocean or when climbing mountain peaks.
