Answer:
The answer is a. Cape Horn in South America, and b. Nicaragua.
Step-by-step explanation:
Before the Panama Canal was finished in 1914, ships sailing in the Atlantic had to navigate to the southermost tip of the American continent, a very long trip, to reach the Pacific. The use of the canal in Panama allowed to reduce the journey by 8,000 miles .
The other option to build the canal was Nicaragua, where a long river, the San Juan river, connects with the huge Lake Nicaragua with the Caribbean Sea. Ultimately, the US decided to build the canal through Panamanian territory and discarded the Nicaraguan option.