Which word correctly completes the sentence: My cousin had a terrible experience _____ she was working for a big advertising agency.

• A. where
• B. when
• C. which
• D. that

Answer: (B)

This tests choosing the right relative word to link a clause that shows time. The experience described happened during a period, so you need a connector that talks about when it occurred. When is the natural choice because it signals time directly: My cousin had a terrible experience when she was working for a big advertising agency. Using where would point to a place, which doesn’t fit the sense of time here. Which or that would refer to a thing, and in this context would sound awkward and not clearly express when the experience happened. So when is the best fit.