Explanation:

- The statement refers to how the secondary sector (industry and manufacturing) dominates China’s economy compared to other sectors.

- The Great Leap Forward (Option 1) was launched in 1958 to fast-track industrialization but led to economic disaster and famine. Its industrial focus set early groundwork despite failures.

- The Reform of 1978 (Option 2) marked the shift to market-oriented policies, opening China to foreign investment, boosting manufacturing, and modernizing the industrial sector.

- Option 3: Both (a) and (b) contributed to China’s industrial dominance. The Great Leap Forward started the emphasis, while the 1978 reforms unlocked massive industrial growth.

- Option 4 is incorrect because at least one (actually both) contributed.

Correct Answer: Option 3 - Both (a) and (b)