Switching from chains to cables in the building of roller coasters was important because cables are less likely to snap when hauling several tons of roller coaster cars full of people. Chains are made of linked, welded pieces of metal that can easily snap if they pull too much. Cables, while they can snap, are much less likely to do so, because they're a stretch of fibers, be it metal or other, without any potential weak spots.
B. Their
There is where something is, and They're is they are
Answer: a couplet
Explanation: In a sonnet, a two line stanza is typically referred to couplet...and it's usually structurally at the ending of the poem...in the case of a fourteen line poem (sonnet).
