Japan's response to gaining control over Manchuria largely involved integrating the region into its empire rather than allowing it to operate independently. Therefore, the most accurate response would be:
It let Manchuria establish its own government and trade policies.
However, while Japan did establish a puppet state called Manchukuo in Manchuria, it was heavily controlled by Japan, and the region did not have genuine autonomy or independent trade policies. Thus, the nuances of these statements could vary depending on the context. For completeness, the statement suggesting Japan pushed American business interests out of Manchuria also reflects Japan's broader imperial ambitions. However, the former option about allowing Manchuria to establish its own policies is often cited in discussions about Japan's colonial governance.