The subject of the sentence is "youngest girl," a singular noun. Although the verb is next to the plural "students," a plural, the verb form must be a singular verb. Additionally, a superlative need a comparison to be used appropriately, making "has dark hair" the correct answer choice.

The issue with the sentence as it is written is that the subject of the sentence, "every night," is singular, but the verb "were" is plural. The subject and the verb must agree. The correct answer is "Every night for five straight nights was well below freezing."

While the singular verb "was" is next to the singular noun "organization," the subject of the sentence is the plural noun "bylaws." This means that the verb "was" needs to be changed to a plural form; therefore, "The new bylaws of the organization were" is the correct answer choice.

Although the verb "hates," which is used with singular nouns, is next to the singular noun "class," the subject of the sentence is the plural noun "boys." The verb needs to be changed to its plural form. Therefore, the correct answer choice is "The boys in the class hate the movie."

Although the plural verb "were" is next to the plural noun "children," the subject of the sentence is the singular "one." A subject and verb in a sentence must always be in agreement regarding number (whether a noun is singular or plural). Therefore, the correct answer choice is "One of the children was late in joining."

The use of "were" is incorrect in this sentence, as the subject is "one," a singular noun. Even though "were" is next to the word "boys," it needs to be a singular verb form. "One of the boys was always coming late to class" is the only answer choice that uses the correct verb form.

The verb used in the sentence, "like," is a plural form, but the subject of the sentence is actually a singular form, "Every one." A subject and verb must always be in agreement. "Every one of the kids likes their new teacher" is the only answer choice to have appropriate subject-verb agreement.

The use of the plural verb form "make" is incorrect in this sentence, as the subject, "The leader," is a singular noun. A subject and verb must always be in agreement, meaning the verb needs to be changed to a singular form. Only "the football players makes all decisions" uses the proper verb form, so it is the correct answer choice.

The subject of the sentence is a singular noun, "first," but the sentence is written with a plural verb, "were." A subject and the verb that describes its action must always be in agreement, meaning this verb needs to be changed to a singular form. The only answer choice to use the correct verb form is "the shows was much tamer."

The verb in the sentence, "were," is a plural verb, but the subject of the sentence is "one," a singular noun. Any subject and verb must be in agreement, so the verb has to be changed to the singular form, because "one" is not underlined in the sentence. Therefore, the correct answer choice is "the boys was making trouble."