Answer: c. specialize in producing beer and export beer.
Step-by-step explanation:
As per the Theory of Competitive Advantage posited by David Ricardo, a country should specialize in the good that it has a competitive advantage in. A country has a competitive advantage if it incurs a less opportunity cost in producing the good.
Opportunity cost of producing beer for Germany = MPLc/MPLb = 2/5
Opportunity cost of producing beer for China = MPLc/MPLb = 1
Germany has a lower cost of producing beer so they should specialize in this and export it.