Final answer:
The biggest threat to China's rapid economic growth is likely to be E. Economic volatility that accompanies fast growth. This threat includes potential economic disruptions from rapid financial inflows and outflows, as witnessed during the Asian Financial Crisis.
Step-by-step explanation:
The question asks which factor poses the biggest threat to China's rapid economic growth. The most significant threat to the fast growth that China is experiencing may not be the increased openness to foreign investments A, the trade isolation by ASEAN countries B, or the reformation of the traditional legal system D. Looking at recent history and considering economic patterns, the biggest threat could be E. Economic volatility that accompanies fast growth. As seen in other East Asian nations, rapid influxes of international capital and subsequent sudden outflows can cause serious economic disruptions, as experienced during the Asian Financial Crisis in the 1990s.
China's continued growth depends not only on its market-based economic reforms and SEZs but also on its ability to avoid the pitfalls that can accompany economic expansion, such as environmental degradation and resource exploitation. Furthermore, maintaining healthy international trade relations, which avoids massive trade deficits and ensures sustained financial inflows, is crucial. Therefore, while options A, B, C, and D present challenges, it is the economic volatility and potential for a sudden reversal of financial inflows that may pose the most significant risk to China's growth.