what is the topic sentence for this passage Ranchers see bolts flash many times among isolated trees or on a strand of barbed wire. Forest rangers manning fire towers report that every thunderstorm brings several flashes to their lofty outposts. Lightning rods are a necessity for radio towers and skyscrapers.
Lightning rods are a necessity for radio towers and skyscrapers.
This is the topic sentence, because it's clear from this that the paragraph will discuss lightning rods and why they are necessary for radio towers and skyscrapers to have. It is broad enough to open the paragraph but also specific enough to give preview and some detail.
