In the U.S., the command-and-control environmental laws of the early 1970s, together with the ensuing amendments and updates that have been made to them over time,

A. were necessary as US industries had zero incentive to control pollution.
B. were an inexpensive incentive for industrial polluters to improve performance.
C. are given considerable credit for cleaner air and water in recent decades.
D. draws distinctions between the needs of firms and costly equipment upgrades.

The command-and-control environmental laws are a set of policies first proposed in the early 1970s that protected the environment by limiting the pollution levels. Also, the government demanded certain changes in production methods or the use of technologies to reduce pollution.

Moreover, these regulations are considered to be the main factor that contributed to the reduction in air and water pollution because since the laws were approved air and water pollution had decreased in the country. Also, it is believed these laws protected ecosystems and natural resources, which contributes to the conservation of nature. Thus, these laws "are given considerable credit for cleaner air and water in recent decades".