Lo+ Adv/Adj + que + verb Que tan /cuan + Adv/ Adj

Question

Hola Inma:Are these
phrases interchangeable?         Lo+ Adv/Adj + que + verb         Que tan /cuan + Adv/ AdjLet's use test question #3 for these purposes:         "¡____
es ese monumento!"Of course the correct answer is:          "¡Lo feo que es ese             monumento!"With regard to this structure (Lo+ Adv/Adj + que + verb) the
lesson states it is used to express surprise/admiration/disappointment
about how something/someone performs an action or about what someone/something
is like. The lesson for the
structure (Que tan /cuan + Adv/ Adj) states that it is used to ASK about
the degree or extent of a specific quality. Yet one of the example is
not a question: "Carlos, muéstrale
a Valentina qué tan bien bailas merengue." The phrase is being used in
regard to a "specific quality," i.e., "... how well... ."

Question:for these purposes,  is not ugliness a specific quality.
(a) if so, could we not also use the structure (Que tan /cuan + Adv/ Adj): ¡Qué
tan feo  es ese monumento! Thank you
in advance.

Accepted Answer

Hola Armando
I understand that as both structures have a similar or even identical translation, this may lead people to think they are interchangeable. 
The qué tan... structure is used as an interrogative and you expect an answer:

- ¿Qué tan tostado quieres el pan?
- Muy tostado, por favor.

Or in an indirect question:
Dime qué tan tostado quieres el pan. Sé que te gusta poco tostado, ¿sí?Tell me how toasted you want your bread. I know you don't like it too toasted, right?
 
 
Here, the structure with "lo" doesn't work:
¿Lo tostado que te gusta el pan? (????)
The structure with "lo" is used in exclamatory sentences:

¡Lo tostado que te gusta el pan! Parece que está quemado...
How tosted you like your bread!/You like your bread so very toasted! It looks like it's burnt...

Saludos cordiales
Inma