What is the arcade in ottonian architecture?

The arcade in ottonian architecture is a succession of arches, each counter-thrusting the next, supported by columns, piers, or a covered walkway enclosed by a line of such arches on one or both sides.
Here is a n example of what the arcade in ottonian architecture look like:
(Personally, to remember this concept, I just imagine it as the inside of a catholic church or temple)

The answer is option c

Howard ruffo  makes the reader feel that ellery has misidentified who is responsible for committing the crime and will end up feeling embarrassed.