Why do writers use appositives and appositive phrases in their writing?

they insisted that there was not enough time to learn everything.  

explanation:

if they were going to steal the answers that is simply because they insisted that there was not enough time to learn everything.  

answer: b) bubbling its way

explanation: an adjective is a word or a group of words that modifies a noun (name, thing, place,

in this case, the first option "to heartily enjoy" isn't describing or modifying any noun, the third option "hiking along merrily" is describing an action but it doesn't modify any noun, the last option "beside us" is just a preposition that indicates position, so the correct answer is the second one: "bubbling its way" because it is modifying the noun "stream".