Choice B is the correct option, in the current MLA format, you finish the quote then add your citation. You do not need a comma to separate the author and page number. Author first, then page number<span />
The answer is "a solution to the problem"
First of all, it is important to define preposition phrase in order to find it in this sentence. We can say that "<span>a prepositional phrase will begin with a </span>preposition<span> and will end with a </span>noun<span>, </span>pronoun<span>, </span>gerund<span>, or </span>clause<span>, the "object" of the preposition"
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*In this case, we find UNTIL TODAY as the only prepositional phrase presented. until is the preposition and today is the noun.