The correct answers are B and D.
B) The Inca road system, known in Quechua language as <em>Qhapaq Ñan</em>, was the largest transportation system in Pre-Columbian South America. It connected important nodes of the Inca Empire following the Andes, from the North in what today is Colombia to the South in what today is Argentina.
D) They also built large stone cities in the Andes mountains, the most famous one among them was Machu Picchu, which is made completely out of giant blocks of stone fitted to each other without mortar.
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For the government: Dissent is unpatriotic and dangerous and must be suppressed. Against the government: Dissent is part of free speech and is healthy in a democracy.
The appropriate answer is B. steam boats could travel against the current on a river. This statement means that steam boats could travel upstream. The steam engine in steam boats allowed them to travel upstream possibly against a strong current. Sail boats rely on wind or the downstream flow of the water to move it from one location to the other. The invention of the steamboat revolutionised transportation of goods and people on large navigable rivers.
