Construction with the finest italian marble, the floor of the church is its greatest attraction and is more attractive to tourists than are its ornate stained-glass windows

(a)..
(b)attraction,itself more attractive to tourists than are its ornate stained-glass windows.
(c)attraction,itself more attractive to tourists as are its ornate stained-glass windows.
(d)attraction,being more attractive to tourists than its ornate stained-glass windows are
(e)attraction as it more attractive to tourists than are the chrch's stained-glass windows


I thought the answer is a, but its b. I could not understand. Please help me.


Thanks,
sen.