If China's economic policy goal is to maintain a weak currency (i.e. avoid the appreciation of the Renminbi to keep export competitiveness) against the US dollar, then the economic policy makers should (mark the CORRECT option):

a. tighten controls on capital outflows

b. Raise the policy nominal interest rate

c. Intervene in the FX market by aggressively buying US dollars and selling Renminbi

d. Intervene in the FX market by aggressively selling US dollars and buying Renminbi