As for this question, when you want to thank someone for the help, it all depends on how that someone has helped you and if the manner that you were helped would also come in as a factor.
When there is immediate contact between the helper and the one being helped, the most direct way to thank someone is to vocalize it and say it to that person that gratitude that you wanted to express. Other ways would be to return the favor to that person. Most people prefer them to be of equal or more than the value of the help given at the moment. If there is no such available way, then what others tend to do is to remain in debt for that person. So when the time comes that the person needs help, they can readily assist and offer the help they needed.
Adjectives and Adverb phrases relate to prepositional phrases because if you remember what an adjective is, it describes a noun and then an adverb i believe can describe a verb, adjective, and other adverbs. Both adjective and adverb phrases contain prepositions, there fore relating them to prepositional phrases.... I hope this is what you were looking for and answered your question... :)
It was caused by an earthquake.
