“___ visit the British Museum while you’re in London, you mustn’t forget to look at the famous Rosetta Stone.”

Options:
a) In case you
b) If you should
c) For fear that you
d) When you might

We’re clearly in a conditional sentence: “If you (happen to) visit … you mustn’t forget …”

• In case you = “because it might happen” (used to explain a precaution) → doesn’t fit.

• For fear that you = “because you are afraid” → wrong.

• When you might = awkward, not used this way.

• If you should = “if you happen to” (formal conditional) → correct.

 Correct answer: b) If you should

“If you should visit the British Museum while you’re in London, you mustn’t forget to look at the famous Rosetta Stone.”