Answer:
B. Increasing atmospheric carbon dioxide will cause mean global temperature to increase by 2 degrees Celsius over the next century.
Explanation:
By definition, a hypothesis is a tentative statement or prediction with little or no experimental test. Hypotheses are always formulated such that they can be rejected if experimental findings are against them.
Hypotheses are predictive and as such, the tone is often in future tense.
From the available options, only option B sound predictive of what might happen in the future.
Hence, the correct option is B.