Explanation: For ships operating exclusively in sea area A-1, the Global Maritime Distress and Safety System (GMDSS) regulations regarding maintenance provisions are designed to ensure safety while acknowledging the proximity to shore. While more distant sea areas (A-2, A-3, A-4) generally require a combination of at least two maintenance methods, for a ship in A-1, only one of the three primary GMDSS maintenance options is required to be in place. These options are: duplication of equipment, shore-based maintenance, or on-board maintenance with a qualified maintainer and adequate spares. Therefore, **C) Only one option for maintenance is required** is correct because for A-1, a single, chosen maintenance strategy from the available GMDSS options is considered sufficient. **A) Carry an on-board maintainer plus duplication of equipment.** This option describes a combination of two maintenance methods. If only one is required, then selecting two, while enhancing safety, is not the *minimum* required provision and thus not the answer to what *must* be had. **B) Shore maintenance may not be selected.** This is incorrect. Shore-based maintenance is one of the recognized GMDSS maintenance options for all sea areas, including A-1. **D) Must always select duplication of equipment to maximize safety.** This is incorrect. While duplication is a valid and often chosen option, it is not universally mandatory over the other two methods. GMDSS allows flexibility in choosing the most appropriate maintenance strategy.