Question

read the passage.
blooms in death valley
in march 2016, death valley national park in california experienced a rare occurrence: thousands of yellow wildflowers covered the region in a \super bloom.\ why was this unusual? death valley is the hottest and driest place in north america. the areas average yearly precipitation is just two inches, making it a challenging place for flowers to grow. however, in october 2015, the valley had received more than three inches of rain in some areas. as a result of the unusually wet season, wildflower seeds that had been lying dormant underground suddenly began to grow, producing an abundance of golden blooms.
what is the main, or central, idea of the passage?
because of an unusual amount of rain, thousands of wildflowers grew in death valley in 2016.
because of the hot, dry conditions in death valley, it is difficult for flowers to grow there.

Explanation:

The passage starts by stating that in March 2016, Death Valley had a "super bloom" of wildflowers. Then it explains that Death Valley is usually hot and dry (average yearly precipitation is just two inches, making it hard for flowers to grow). But in October 2015, there was more than three inches of rain in some areas. As a result, the dormant wildflower seeds grew. The first option directly ties the cause (unusual rain) to the effect (wildflowers growing in 2016), which is the main idea. The second option is just a supporting detail about the usual conditions in Death Valley, not the main idea of the "super bloom" event described.

Answer:

Because of an unusual amount of rain, thousands of wildflowers grew in Death Valley in 2016.