Final answer:
The Lewis and Clark expedition collected numerous plant and animal specimens and detailed the geography of the West, although they failed to find a Northwest Passage. The correct option is A. they were able to send back several specimens of the new species they discovered.
Step-by-step explanation:
One significant outcome of the Lewis and Clark expedition was that they collected and sent back hundreds of plant and animal specimens, some of which were new to science and were subsequently named in their honor. Additionally, the expedition aided in more accurately mapping the territory and helped solidify the United States' claim to this vast territory.
While they established peaceful relationships with many Native American tribes, they also engaged in a hostile encounter with the Blackfeet tribe, which resulted in the death of two Blackfeet men. However, the majority of interactions with Native Americans aimed at asserting American power while maintaining peace.
It is important to note that they did not discover an all-water route to the Pacific, as none exists, but their achievements were quite notable, including detailed documentation of the geography and biological specimens of the West. The correct option is A. they were able to send back several specimens of the new species they discovered.