Test analysis: Science is an internal whole, and any part of it is a complete chain, which shows that the objective world is an objective existence independent of human will. (2) In "Du", the expression is too absolute, so don't choose. Truth is objective, concrete and conditional, ③ Don't choose. 4 in line with the problem. Choose a for the correct answer to this question.

Test center: This question examines the materiality of the objective world.