Why did the United States introduce the Marshall Plan in the post-war era? to stabilize Europe and support democratic governments
to encourage Europe to share its post-war prosperity with the United States
to help the USSR in forming a democratic government
to boost economic recovery in the United States following World War II

The objectives of the United States were to rebuild those areas destroyed by the war, eliminate barriers to trade, modernize European industry and make the continent prosperous again; all these objectives were intended to prevent the spread of communism, which had a large and growing influence in post-war Europe

d) a constitutional amendment

the underground railroad (apocope of the metropolitan railroad) is a system of urban trains located within a city and its metropolitan area. it is characterized for being a massive transport of passengers in the big cities, uniting diverse zones and their environs, with high capacity and frequency and in segregated form to other systems of transport. metropolitan railroads are built underground or on the surface, although most systems use mixed models where sections are combined in both modalities.

1 - as a result, the metro tends to reduce car travel for two reasons: first, due to the greater transfer of users from the car and, second, due to the reduction in the acquisition of cars in homes located in sectors near the stations of the metro.

2 -the metro allows to contribute effectively to the achievement of all the objectives of an urban development policy: it improves the efficiency of the city's economy by reducing travel costs and also generates a higher level of activities in the city center, taking advantage of of the agglomeration economies.

3 -it is a clean means of transport, since it uses renewable energy (usually electricity), taking care of the environment and avoiding excessive pollution.