Sentence Correction

pink_08 wrote:Ron, I saw your comment that "as" is used for prepositional phrases. Is this an exception to the general rule that as is only used to introduce clauses.

well, you've got to remember that "as" is not ONLY used to introduce clauses. it is used:
(1) to introduce clauses;

(2) to introduce prepositional phrases (as in the problem you've posted) <-- note that "as" is used in this way HERE

(3) to state that a person/thing is acting in a particular function/capacity (see #49 in the OG11 or OG12 DIAGOSTIC section),

(4) in a COMPARISON ("as soft as a baby's skin"; "three times as loud as a rock concert")

--

it seems that you're making this more complicated than it needs to be. in general, if a particular word/phrase/construction can do thing #1, thing #2, thing #3, and thing #4, you should just memorize all four of these things separately - there's not much point in construing things #2, #3, and #4 as "exceptions to thing #1".
especially in the case of words like that and as - which have huge numbers of possible uses - that sort of approach is going to be unnecessarily painful.

money9111 wrote:going further with the comparison.. isn't it also true that "as" can't be used to compare two things? in that instance you should use like?

LIKE vs AS is more of a grammatical issue than anything else.

when you make a comparison with LIKE, you're comparing nouns (or noun phrases, or anything else that acts like nouns). for instance, my brother is like my cousin.

when you make a comparison with AS, you're comparing actions/clauses or prepositional phrases.
alternatively, if you use the separate idiom as ADJ/ADV as..., then you're comparing the quality described by that ADJ/ADV.
for instance,
james has been accepted to several business schools, as has his twin brother.
in 1968, as in 1964, smith won three medals in the summer olympic games.
the baby's skin is as soft as chamois.

etc.

note that all of these sentences are, technically, "comparisons" (although, again, it's not the best idea to run around trying to stick labels on too many things).