The error in the original sentence is that the word "that" cannot modify people. "Who" must be used to refer to the mugger. 

Because the word being chosen is referring to a group of people ("students"), you need to use "who."

The use of "itself" in the sentence is incorrect. "Itself" is a referential pronoun, and as the word is used as the subject in a complete though, there is nothing to refer to therefore, the correct answer is "bit it is a skill."

This sentence contains a pronoun usage error. The word "who" is meant to refer to company, but is never use to describe non-human words. The appropriate choice is "which," making the correct choice "which was considered quite aggressive in the industry."

This sentence contains three errors: two pronoun errors and a verb voice error. First, the pronoun "who" can never be used to describe non-humans (additionally, even if this was correct, the proper form would be "whose," not "who's." The appropriate word is "which." Additionally, the clause contains a passive voice verb (the subject of the clause is not doing the action of "developed"). The correct choice is, "which have developed economies," which fixes all of these issues.

This sentence misuses a pronoun. The correct answer is, "Anne was walking to her friend's house" since it is the most clear and concise. Using "their" makes it ambiguous as to whether the sentence is saying that Anne is heading to the house that she shares with someone else (In this case, the person would need to be mentioned before using "their") or if she is just going over to someone else's house. The use of "the" in this place is equally vague (It begs the question "whose friend?") and "she's" is not the proper form.

This sentence misuses the pronoun "who's." This word is a contraction for "who is." The appropriate form is "whose." The correct choice is, "Whose wallet is this?" The other choices contain errors in pronoun usage and dangling prepositions.

This sentence contains two pronoun errors. First, "who" is not the appropriate pronoun because it refers to "product," which is a non-human noun. All non-humans are referred to with the pronoun "which" in English. Furthermore, the usage of "they" is incorrect, since it refers to the word "company," which is grammatically singular, even though it possibly refers to many individuals. The correct choice is, "The company planned to dominate the market with its new product, which it nicknamed "Project Zero." "

This sentence misuses the pronoun "whose," which is possessive. It is clear from the context of the sentence that "who was" should be in this place. The correct choice is, "to determine who was responsible for the accident." Note that the choices with "he was" and "what person was" are wrong because the first is imprecise and ambiguous (it is typical to mention a person or thing by name before using he, she, or it) while the second is less concise.

The sentence presented uses a reflexive pronoun, "myself," that does not refer back to anything previously mentioned. The proper form would be the standard pronoun "me," which is the correct answer.