GMAT Sentence Correction (SC) | Re: The westinghouse air brake, first demonstrated successfully in 1868, h

Hi Mike,

Thanks for your explanation. I chose wrong option on practice test for the following reasons :

1. I couldn't split between 'whereas' and 'but'. I ignored because both show contrast to some extent. There are other officials problems in which the ans choices are split between words (or conjuctions) which convey the same meaning but may not fit in given context for one or other reason. Any safer approach to avoid such traps?

2. I rejected B because I couldn't rationalise whether past