Congress lacked the money it needed to pay off the government’s war debt because it could not regulate trade with foreign nations the national currency was too weak it could not levy taxes to raise revenue the money was used to prevent internal rebellions

The correct option is "the national currency was too weak"

While the Southerners resigned their seats in the Senate and the House of Representatives, secession allowed the Republicans to approve proposals that had been blocked by the Southern senators before the war. Among these laws that were approved highlighted the Morrill Act, through which the important iron industry was protected; the Homestead Act, according to which all free citizens who applied for 160 acres of land not yet worked from the territories outside the Thirteen Colonies would be granted; the construction of a transcontinental railroad; the National Banking Act, with which the use of the national currency was developed and the Law of Legal Course of 1862, which authorized the use of bank notes. Fees on income to finance the war were also approved with the Tax Act.