Ideally, a patent should cover a long enough period of time for the inventor to but that period should not be so long that it allows the inventor to
a. earn a hearty return; charge a high monopoly price permanentlyb. contribute to the social interest; only receive a slice of the social benefitsc. earn a rate of return; prevent broad public access to classic worksd. contribute to the social interest; prevent broad public access to inventions

option A.

Explanation:

The correct answer is option A.

A patent should cover a long enough period so that the inventor can earn a hearty return.

the period should not be so long that it allows the inventor to charge a high monopoly price permanently.

When researcher invents something new then they can patent the technology.  

By patenting the technology the scientist can earn money if the people use his technology.

1. Nationalism

2. Urbanization

3. Prohibition

4. Disarmament

5. Open Door Policy

6. New Deal