Answer:
The stereotype about doctors that emerged during the industrial and scientific revolution was that they would sacrifice anything for the pursuit of knowledge.
John snow first discovered cholera by doing a research is a big city in London and he find out that people in those areas were drinking contaminated water and he discovered cholera in 1854.
The correct answer is D. This sentence is a perfect example of parallel structure because either after and before AND it in both cases uses simple past tense verbs which are LEARNED AND TRAVELED. The other sentences never show parallelism due to their units are never the same. For example, in letter A , it uses a verb in simple present WALKS AND a progressive tense verb which is TAKING. So, to sum up, for a sentence to be considered parallel, it must be coherent in its structure and internal words. They need to have harmony and unity in tenses as well.
