The question that would best help a scientist determine if a space object is a comet, asteroid, or meteoroid is:
Does the space object have a tail when it nears the Sun?
This question is particularly relevant for differentiating between comets and asteroids. Comets develop tails when they approach the Sun due to the sublimation of their ice and the release of gas and dust, whereas asteroids typically do not have tails. Meteoroids are generally smaller fragments and may also not have tails, but they are often classified based on their size and origin rather than the presence of a tail.