Answer:
In the sentence "This is the best one of the articles about Pocahontas that I found", the demonstrative pronoun is "this".
Step-by-step explanation:
Demonstrative pronouns are words used to indicate items in space or time. They can be singular (this and that) or plural (these and those). They refer to something that is close in time and space (this and these) or distant (that and those).
In the sentence we are studying here, the demonstrative pronoun "this" substitutes the noun "article". If the speaker uses "this", we may assume that the article he/she refers to is close in space to him/her.
Note: This, these, that, and those can also function as demonstrative adjectives. Instead of substituting a noun, they accompany and modify it. if the sentence were "This article is the best one of the articles about Pocahontas that I found," "this" would be a demonstrative adjective modifying the noun "article". But, in the sentence we're working with, it is a pronoun, substituting the noun.