For me, both B and D make sense. Do you have any text I can read?
The present-day civil struggle in Algeria is very complicated and has deep origins, but in general it was political rivalries that were in part set off by colonizers.
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.
One of them is A, because Nubia and Egypt both ruled over each other at different times.
B. the dropping of the atomic weapons demonstrated the potential power of each bomb, leading the Japanese to surrender in order to protect the remaining civilian population.
