Final answer:
The fallacy in this argument is Appeal to Popular Belief, also known as a bandwagon fallacy. This fallacy occurs when someone argues that something must be true or valid because a majority of people believe in it.
Step-by-step explanation:
The fallacy in this argument is Appeal to Popular Belief, also known as a bandwagon fallacy. This fallacy occurs when someone argues that something must be true or valid because a majority of people believe in it. In this case, the argument assumes that because 90% of the world believes in some form of a higher being, God must exist. However, the popularity of a belief does not necessarily make it true.