Which type of ladder can be converted from a straight ladder to an A-frame configuration?

A combination ladder is designed to provide versatility by allowing it to be used in multiple configurations. When you convert a combination ladder from a straight ladder to an A-frame configuration, it enhances stability and usability for various tasks, such as accessing elevated areas or providing support for working at height.

The A-frame configuration is particularly useful for scenarios where mobility and stability are crucial, such as during firefighting operations or when accessing structures at a sloped angle. This adaptability makes the combination ladder a valuable tool for firefighters, as it can meet the demands of different situations without needing multiple types of ladders.

Other types of ladders listed, such as the Boston ladder, attic ladder, and Bangor ladder, have specific designs or intended uses that do not offer the same level of adaptability as a combination ladder. Each of those alternatives serves distinct purposes, but they lack the dual functionality feature inherent in a combination ladder, making the latter the correct answer for this question.