B) The daily work continued; nay, it actually increased;
Something that is happening on a consistent basis. It also gives the feeling that it is work to make it persistent. In option B, the statement "daily work" indicates that something is done daily which supports the idea of persistent. The sentence containing the line "The daily work continued; nay, it actually increased" also includes the description "with an astonishing pertinacity." Pertinacity means persistent determination. The brain failing and life slipping away does not show any persistent determination. Also, the statement that she inquired with acute anxiety does not how any persistent determination.
The correct preposition that you should add to make the sentence correct is TO. The answer is then "To facilitate a quick getaway, the cunning thief parked the car perpendicular to the building". Perpendicular things always have the preposition TO next to them.
Unfairly because racism is that the answer you want