When Straddlers enter white collar jobs, they get lost because:
Straddlers are thrown into a system which is foreign to them (option a) - this is the key idea conveyed by the author in the last three paragraphs. Option (b) clearly holds no meaning considering the theme of the passage. On reading the 4th paragraph, option (c) might not always be true. While option (d) is true, it is not the primary explanation as to why Straddlers get lost after entering white-collar jobs.
Hence, the correct answer is option (a).