Outside city limits, the minimum distance for parking cars from a warning cross indicating a railroad crossing is 50 meters (165 feet).

a. true. b. false.

The answer is c - the principal of original lateral continuity. 

Answer heart of american                  live in harmony                    hillsides of orchards                    blaze of color                    backdrop of pines;

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Answer

it is the minimum amount of material needed to sustain a fission reaction.

explanation

critical mass is the minimum amount of fissionable material that must be assembled for a sustained fission reaction to take place. although two to three neutrons are produced for every fission, not all of these neutrons are available for continuing the fission reaction. if the conditions are such that the neutrons are lost at a faster rate than they are formed by fission, the chain reaction will not be self-sustaining.   at the point where the chain reaction can become self-sustaining, this is referred to as critical mass.