The correct sentence is:
c) There’s always a terrible traffic in Los Angeles.
This sentence is grammatically correct and conveys the intended meaning. The use of the word "terrible" to describe the traffic in Los Angeles effectively communicates that it is consistently bad. The verb "is" is correctly contracted to "there's" to indicate the existence of the traffic. Overall, this sentence follows standard English grammar rules and effectively expresses the idea that traffic in Los Angeles is consistently terrible.