Question

add the sentence that best establishes the topic of the paragraph.
each november, the meteor shower occurs as particles from the comet tempel-tuttle enter earths atmosphere, burning up and appearing as streaks of light. in a typical leonid shower, only about fifteen meteors appear per hour, one of the lowest rates of any major meteor shower. nonetheless, every thirty years or so, people can expect to be dazzled by a leonid \storm.\ in contrast to a meteor shower, a storm produces at least one thousand meteors every hour. a particularly breathtaking leonid storm took place in 1966, when thousands of meteors fell per minute as earth traveled through an unusually dense cloud of particles from tempel-tuttle. stargazers remarked that the streaks of the meteors resembled a giant waterfall.
the leonids meteor shower gets its name from the constellation leo, the lion, which is located near where the meteors appear to originate in the sky.
the meteor shower known as the leonids isnt the most active or powerful of the year but occasionally produces an astonishing display.
although astronomers cannot count the exact number of meteors that appear in a leonids meteor shower, they can make educated guesses.
the leonids meteor shower is best viewed on a clear night, but increasing light pollution is making this cosmic event difficult to see.

Explanation:

The paragraph discusses the Leonids meteor shower, including its typical low meteor rate and occasional spectacular "storms." The second option ("The meteor shower known as the Leonids isn't the most active or powerful of the year but occasionally produces an astonishing display.") effectively captures both aspects (regular low - activity and occasional amazing shows) which are the main themes of the paragraph. The first option only focuses on the name origin, the third option is about counting meteors (not the main topic of the paragraph), and the fourth option is about viewing conditions (not the main focus).

Answer:

The meteor shower known as the Leonids isn't the most active or powerful of the year but occasionally produces an astonishing display.