"notice of a proposed federal regulation in the federal register need not contain: a. the environmental impact of the proposal b. the name of the proposing agency. c. the language or the proposed rule or a summary. d. the statutory authority for promulgating the rules."

a. the environmental impact of the proposal

Explanation:

              The Federal register of the United States is the official register of the federal Government of U.S. which contains all the rules and regulations of the various government agencies, public notices,etc. It also contains the proposed rules in the federal government.

              The  proposed federal regulation contains the name of the government agency that has proposed the rule, the summary of the proposed rule and the language. It also contains statutory authority for promulgating the rules.

Thus The Federal Register does not contain

a. the environmental impact of the proposal

you answered your own : -/