In the sentence above, because the initial noun used is "girls" we know that we are dealing with a group of girls. Therefore, later in the sentence, the corresponding noun "astronaut" should be plural. The best way to correct the underlined portion of the sentence above is: "all hoped to grow up to become astronauts."

In the sentence above, because the initial noun used is "members of the jury" we know that we are dealing with a group of people. Therefore, later in the sentence, the corresponding nouns "its mind" should be plural. The best way to correct the underlined portion of the sentence above is: "could not make up their minds about the trial."

In the sentence above, because the initial noun used is "candidates'" is later referred to by a singular phrase "that interviewee."  Since there is no option to replace the singular noun, we know that the candidate in the inititial sentence is meant to be a singular candidate, and as it is written, it's a plural candidate.  The best way to correct the underlined portion of the sentence above is: "the candidate's personality."

In the sentence above, because the initial noun used is "men" we know that we are dealing with a group of men. Later in the sentence, the corresponding noun "assistant" should be plural. The best way to correct the underlined portion of the sentence above is: "grateful to be the assistants to such a great man."

In the sentence above, because the initial noun used is "stars" we know that we are dealing with a group of stars.  Therefore, later in the sentence, the corresponding noun "player" should be plural.  The best way to correct the underlined portion of the sentence above is: "and were not the players they could have been thereafter."

Because the subject of the sentence ("children") is plural, it is presumed each child has their own basket and is looking for eggs. For this reason, the nouns "basket" and "egg" both need to be plural.

In the sentence above, because the initial noun used is "Paul" we know that we are dealing with an individual. Therefore, later in the sentence, the corresponding noun "knights" should be singular. The best way to correct the underlined portion of the sentence above is: "he was set on becoming a great knight."

Note that a colon is correctly used to join two independent clauses, where the second clause explains or clarifies the first.

In the sentence above, because the initial noun used is "amateurs" we know that we are dealing with a plural subject. Therefore, later in the sentence, the corresponding noun "performer" should be plural. The best way to correct the underlined portion of the sentence above is: "The amateurs wouldn't grow up to become great performers:"

Several amateurs cannot become one great performer (at least with how technology stands at this juncture of history).

In the sentence above, because the initial noun used is "charges" we know that we are dealing with a group of recruits. Therefore, later in the sentence, the corresponding noun "student" should be plural. The best way to correct the underlined portion of the sentence above is: "All four of Mariah's charges were excellent students,"

"All" is a pretty good indicator that a plural pronoun will need to be used.