Does anybody know the explanation for this? By the way, the answer is “riveting”.
We are looking for a word that has similar meaning to captivating due to the line cult of criminals which carries the idea of making someone completely engrossed into something (Here, WH is afraid after reading Dicken’s Oliver twist people will be completely engrossed by thieves.)
But riveting, by no means, means engrossing. Does it?
Sorry my bad 
In simpler math strategy, it comes down to this, LHS keyword is Dangerous, criticized is our div word unobvious word with negative connotation ,
Dangerous (-). Criticized(-). ?
negative * negative = positive
RHS has to be positive, from the options the only option that is positive is riveting which means interesting
@Ram I am afraid your explanation might be slightly wrong because the word criticized is already on the RHS.
@ralbusg I see that your div word is “that”. Your interpretation is not wrong, but we can also take criticized as div word, it works either ways if “that” is taken as div word, we cant ignore “criticized” on right so, just like your process RHS becomes “criticized ____” as RHS has criticized, blank has to be positive.
Even I did the same thing but eliminated that extra step of contrast * positive = contrast on RHS altogether as I took criticized as division word.