Step 1: Sentence 4 establishes electricity as the main power source for industries. The next sentence should logically expand on how electricity is produced or the challenges associated with it.
Step 2: Sentence D, starting with "but," introduces a challenge: electricity production requires huge quantities of coal, making it a natural continuation of sentence 4.
Step 3: Sentence A continues the discussion of electricity production methods, mentioning that electricity from water (hydropower) requires costly river valley projects, adding another challenge.
Step 4: Sentence C, starting with "besides," adds another issue: the depletion of mineral resources (like coal) needed for electricity generation, building on D and A.
Step 5: Sentence B, starting with "in contrast," offers a solution by introducing atomic power stations as a cost-saving alternative, leading to sentence 6, which advocates for atomic plants to address resource shortages.
Step 6: The sequence DABC creates a logical flow: electricity’s importance (4), coal consumption issue (D), hydropower cost issue (A), resource depletion (C), atomic power solution (B), and conclusion (6).
Verification: Other sequences like BDAC disrupt the flow (e.g., B’s solution appears too early), and CDAB starts with resource depletion without context.