Which of the following claims can be tested by scientific means?

a. People born when the Sun is in the constellation of Leo are more financially successful than other people.
b. The final thoughts of Abraham Lincoln were about the fate of his country.
c. God exists.
d. Blue is the best color for walls.

a. People born when the Sun is in the constellation of Leo are more financially successful than other people.

Explanation:

Option A is the only claim that could be tested by scientific means. In this kind of a scientific study, we would need participants who were born when the Sun was in the constellation of Leo. We would then measure their financial success, in order to prove whether there is a particular correlation between the two. Other claims cannot be tested. For instance, we can never know what the final thoughts of Abraham Lincoln were, nor can we know whether God exists - some people chose to believe that he does and other that he does not. The question of whether blue is the best wall color depends on our personal preferences, and there is no universal answer.

whichever one it is, it's definitely not one that you included on the list you provided.

none, its a machine