The correct answers are C) science can explain everything.
The notion that was challenged by the work of postwar-era scientists was that science can explain everything.
Scientists in the postwar-era began to question the premise that science can explain everything. Although science uses the scientific method to prove the existence of things, postwar scientist realized that not always science had all the elements to explain certain things that philosophy or logic could explain better.
The other options of the question were, a) there are no answers, b) accuracy is impossible, and d) scientific theories reflect reality.