Re: Why do you think other people believe in God?
Other people believe in "God" because of a variation of each of the 5 poll items and then some. Probably the most decisive factor regarding a person's beliefs is how they were raised. This is statistically obvious when you look at the various belief systems of the world and their demographics. As a general rule, if you are raised in a Muslim family you believe in the Muslim God, if you are born into a Jewish family, you believe in the Jewish God, etc. This phenomena is observable for nearly every religion throughout the world. I also believe that it is also observable to some degree for non-religious beliefs such as political/philosophical beliefs and even among non-theistic beliefs such as atheism.
As a person ages, I believe that the other poll items may either confirm and strengthen their beliefs, or if a lack of confirmation comes, then that person may entertain new beliefs about god.
Statistically, it appears that most often, a person raised in a certain belief comes to an affirmation (rather than denial) of their beliefs based on such things as a desire for comfort and meaning in life (item #1). This is understandable, based on the fact that most belief systems make pretty favorable claims and promises for the believers within those systems. In light of what one must give up upon renouncing one's beliefs, I can see the possibility that some psychological mechanism would work very hard to prevent that from occurring after years of such beliefs.
I thinks that items #3 (exposure to science) and #5 (arguments from design) are closely related. I think that a person who has had a minimal exposure to science and has been raised under a belief system that teaches design will gravitate toward accepting arguments from design as evidences for their beliefs. This again is probably quite natural. Why would a person who is raised with a certain world-view choose to disregard it without some external influence prompting them to do so? Without the exposure to science, one of the major influences of challenging world-views based on faith has been silenced.
Regarding item #2, fear and hope are always great motivators. Depending on the psychology of any given individual, these will play varying roles in why a person believes in God. There are some people who have their prime motivation for belief grounded in their fear of going to "hell", so obviously fear can be a strong influence.
For those who have grown up with minimal influence regarding belief or disbelief in God, then I would say that item #1 would play the primary role in whether a person chooses to accept a theistic belief system or not.
My 2 cents worth...
By the way I voted for #4 - "Raised to Believe in God."