Question

human activity and earthquakes
when americans think of earthquakes, they tend to think of california, a state known for its frequent seismic activity. in recent years, however, people in arkansas, colorado, kansas, new mexico, oklahoma, and texas have been feeling the ground shake more often. an increase in oil and gas drilling in these states has led to \human - induced\ earthquakes—those resulting from human activity. when wastewater is disposed of during gas and oil drilling, the water is forced deep underground. the resulting buildup of pressure can cause fault lines (cracks in the earths crust) to shift. according to mark petersen, head of the u.s. geological surveys earthquake hazard mapping project, \in the past five years, the usgs has documented high shaking and damage in areas of these six states, mostly from induced earthquakes.\
what is the main, or central, idea of the passage?
an increase in oil and gas drilling has caused a corresponding increase in earthquakes in six states.
residents of six u.s. states have experienced an increase in earthquake activity in recent years.

Explanation:

The passage starts by contrasting the common perception of California for earthquakes with recent increased shaking in six states (Arkansas, Colorado, Kansas, New Mexico, Oklahoma, Texas). It then explains that the increase in oil and gas drilling (human - induced factor) is the cause. The USGS data (from Mark Petersen) further supports that the high shaking and damage in these six states are mostly from induced earthquakes. The first option directly ties the cause (increase in oil and gas drilling) to the effect (increase in earthquakes in six states), which is the main idea. The second option only mentions the increase in earthquake activity without highlighting the cause (human - induced due to oil and gas drilling), which is a key part of the passage.

Answer:

An increase in oil and gas drilling has caused a corresponding increase in earthquakes in six states.