OE
You might feel stuck if the idiom “groan under the strain” isn’t familiar to you, but process of elimination can still work here. The part of the sentence following the colon must be equivalent—either an example or a restatement—to the part before it. The word that fills the blank must make “city infrastructure is already _________ under the strain of excess auto traffic” a good reason to create bike lanes in the city. Since bike lanes would help to relieve the traffic burden, the blank must mean something like struggling. “Groaning,” which is something that a person struggling with a heavy load would do, is used figuratively here. The words “seething” (very angry), “waiting,” “baying” (yelling loudly), and “intensifying” don’t create an image of a person struggling under a heavy load the way that “groaning” does and so are not correct.
Answer: C