Answer:
3. Why is the weather in San Francisco different than the weather in San Jose?
Explanation:
Writing a good researc paper includes several steps.
One should first make an observation, conduct a research, identify the topic, suggest a hypothesis and provide an evidence supported explanation.
The topic should be chosen in a manner that it can provide answers to how or why something happened (or happens).
Proper use of scientific method is essential.
Answers 1. 2. and 4. are simply questions regarding facts. They don't require any research or experiment to be conducted.
Only answer 3. is a question based on an observation and in order to answer it, one needs to do some research and set a hypothesis and prove whether it is true or false.