Question

A?
http://prntscr.com/5vwkmv

Answer 1

An octagon is concrete, not abstract, I think - it's tangible, and you can touch it. Also, I think it's countable: you can have 3 octagons, for example. An abstract, uncountable thing would be something like love - it is intangible, and you can't count it (you can't have 3 loves).

Answer 2

So B? o-o

Answer 3

Yep, I'd go with B!

Answer 4

Okay, thanks.