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 introducing the rare "super bloom" in Death Valley in 2016, then explains the usual dry conditions, and finally attributes the bloom to the unusual rain in 2015. The first option captures the main event (wildflowers growing) and its cause (unusual rain), while the second only describes the usual difficulty for flowers, not the main event of the bloom.

Answer:

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