A. Maybe every travel guide that contains references to Italy recommends that tourists, especially those in search of a romantic atmosphere, visit the"floating", uniquely beautiful
The part of the sentence "that contains references to Italy" requires a comma to seperate it from the rest of the sentence, so that "every travel guide" can connect directly with "recommends that". Incorrect option.
B. Every travel guide containing references to Italy recommends that tourists, especially those in search of a romantic atmosphere, visit the"floating", uniquely beautiful
Changes the meaning of the sentence by not including the word "maybe" or "perhaps". Incorrect option.
C. Perhaps every travel guide containing references to Italy recommends that tourists, especially those in search of a romantic atmosphere, visit the uniquely beautiful, "floating"
Correct option.
D. Perhaps every travel guide that contains references to Italy recommends that tourists, especially those in search of a romantic atmosphere, visit the "floating" city, uniquely beautiful
Same as option A. Also the word "city" is repeated twice, making the parallelism incorrect. Incorrect option.
E. Perhaps every travel guide that contains references to Italy recommends that tourists, especially those in search of a romantic atmosphere, will visit the "floating", uniquely beautiful
Same as option A. Also change of tense from simple present to simple future, is unnecessary. Incorrect option.