The determination of the objects of the underlined prepositions are as follows:
1. The object of the preposition "from" is C. volcano.
2. The object of the preposition "with" is B. approval.
3. The object of the prepositional phrase "in front of" is B. library.
4. The objects of the preposition "about" are B. river and C. animals.
In grammatical expressions, an object is the direct or indirect receiver of the verb's action. An object can be identified by questioning the verb with "what?" or "whom?".
Thus, the objects of the underlined prepositions are determined as above.
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