And thus for a time I was occupied by exploded systems, mingling, like an unadept, a thousand contradictory theories and floundering desperately in a very slough of multifarious knowledge, guided by an ardent imagination and childish reasoning. . . A slough is a place of deep mud. Why does the author use the word slough in the line?

a) the author felt trapped
b) the author felt free
c) the author felt he had won
d) the author felt dirty