13. You must stop at the intersection ahead. Just before the intersection, you have to cross railroad tracks. You should stop before you cross the railroad tracks when:

Answer dependency ratio;

Answer/// the transcontinental railroad wasn't completed until four years after the civil war ended, it wouldn't have made much of a difference if it was completed before the war as it only ran east to west not north and south,   the first battle between iron-clad ships took place during the civil war (1862) it made wooden naval ships obsolete. the gatling gun was invented during the civil war , it was the forerunner of modern machine guns;

Answer8 months;

Answersocial mobility;