B. It is not raining.
We know that no rain = the shuttle takes off. The conclusion tells us that the shuttle took off. In order for that to happen, the weather cannot be rainy. Therefore, the minor premise is that it is not raining.
This problem is a syllogism. A syllogism is a form of deductive reasoning in which a conclusion is formed looking at two different premises. In the example the major premise tells us the parameter of the situation. The minor premise tells us the condition. The conclusion tells what is true based on the two premises.
