Which statement explains how two causes combined to create an effect, which became the great depression?

a) high tariffs decreased imports, which led foreign investors to withdraw large amounts of money from american banks.
b) overproduction led to increased exports, which shifted investment to foreign countries and dried up the credit available to american consumers.
c)the excessive use of credit allowed consumption to increase rapidly, which stimulated production to the point that it outpaced demand.
d)buying on margin allowed american investors to send their money abroad, which resulted in a political backlash that led congress to increase tariff rates.

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.