The statement that shows the significant challenge in building the panama canal.
a. frequent rains caused rivers to flood.
b. engineering plans were often wrong.
c. workers went on strike to get extra pay.
d. congress did not provide enough money.

The biggest challenge in building the Panama Canal was malaria & yellow fever. This caused many deaths of the workers. However, that statement is not given here. So the next significant challenge in building the Panama Canal was frequent rains caused the rivers to flood. There were snakes, impassible jungle, so many things went wrong with the building of the canal. The correct answer will be A.