1. For A, the sentence requires a noun to complete the phrase "famous for A old monastery". The best fit is "their" which refers to the islands.
2. For B, the sentence describes what visitors do. "see" is the correct present tense verb to complete the infinitive phrase "to see".
3. For C, the sentence describes an action happening in the past while the speaker was there. "was listening" is the past continuous tense, fitting the context.
4. For D, the sentence describes a general truth about people who visit. "Everybody" fits the context of a general statement.
5. For E, the sentence describes the availability of shops. "a few" indicates a small but countable number of shops.