Inventors in developing countries are usually unable to capture the full benefit of their innovations. They therefore tend to devote too few resources to research. Government can address this problem of under-investment in research by (i) increasing restrictions on trade; (ii) establishing a patent system to provide inventors with exclusive control over their inventions for a period of time; (iii) subsidising the purchase of technology from other countries. a. only (i) is used.
b. only (ii) is used.
c. only (iii) is used.
d. (i), (ii) and (iii) are all used.

4. understanding different policy options to correct for negative externalities carbon dioxide emissions have been linked to global warming. the following table lists some possible public policies aimed at reducing the amount of carbon dioxide in the air. for each policy listed, identify whether it is a command-and-control policy (regulation), tradable permit system, corrective subsidy, or corrective tax. public policy command-and-control policy tradable permit system corrective subsidy corrective tax the government charges factories $110 for every ton of carbon dioxide they emit. the government orders every factory to adopt a new technology, which reduces carbon-dioxide emissions into the atmosphere. trees take carbon dioxide out of the air and convert it to oxygen, so the government funds a tree-planting initiative by offering $110 to any citizen who plants a tree. the government limits total carbon-dioxide emissions by all factories to 180,000 tons per month. each individual factory is given the right to emit 140 tons of carbon dioxide, and factories may buy and sell these rights in a marketplace.