The correct answer is they saw Germany as the greatest threat.
The Allies agreed to focus on Europe before Asia during World War II because they saw Germany as the greatest threat.
The Allies –basically the United Kingdom and the United States- planned a strategy during World War II that was focused on attacking Germany before Asia. They named the strategy “Germany First”. After Winston Churchill and Franklin D. Roosevelt conversations on the “Germany First” strategy, both countries focused their war efforts on defeating Germany, that was considered the main threat of the soverignty of England.
The other options of the question were, b) Japan was too strong at the time to fight, c) Japan was showing signs of asking for peace, and d) they had more resources in Europe.