A.I. Explanation:

Option 1: "Lack of interest in renewable energy sources"

Explanation: The text does not mention a lack of interest as a challenge. Instead, it highlights that countries are actively striving to reduce carbon emissions and combat climate change, indicating a strong interest in renewable energy.

Option 2: "Difficulty in finding suitable locations for wind farms"

Explanation: While the text discusses wind energy, it does not identify location difficulties as a challenge. Instead, it focuses on offshore wind farms contributing significantly to energy production, suggesting that suitable locations are being utilized.

Option 3: "High initial costs of setting up renewable energy projects"

Explanation: The text mentions that solar power is increasingly cost-effective, which implies that high initial costs are not a primary challenge. The focus is on the viability of renewable energy options rather than their costs.

Option 4: "Energy storage and infrastructure investment needs"

Explanation: The text explicitly states that challenges such as energy storage and the need for substantial infrastructure investment remain in the transition to renewable energy. This aligns directly with the question, making it the correct answer.