A.I. Explanation:

Option 1: "To provide a quieter and smoother ride"

Explanation: While the text mentions that electric buses offer a quieter and smoother ride compared to traditional diesel buses, this is a secondary benefit rather than the primary purpose. The main focus of the text is on combating climate change, which is not addressed by this option.

Option 2: "To expand the city's cycle lanes"

Explanation: This option is incorrect because the text specifically states that London has expanded its cycle lanes, but it does not link this action to the introduction of electric buses. Therefore, this option does not reflect the primary purpose of the electric buses.

Option 3: "To promote car-sharing schemes"

Explanation: This option is incorrect as the text discusses car-sharing schemes as a separate initiative. The introduction of electric buses is not aimed at promoting car-sharing, making this option irrelevant to the primary purpose.

Option 4: "To reduce carbon emissions"

Explanation: This option is correct because the text explicitly states that the introduction of electric buses aims to reduce carbon emissions significantly. This aligns directly with the primary purpose of introducing electric buses in London, which is to combat climate change.