In the original sentence, the verb "knows" is in the incorrect mood—the indicative. Because of the word "that", we know the sentence contains an order, which means that we must change the verb to the subjunctive mood ("know"). 

The phrase underlined in the sentence uses the modal verb "can," which conditions what might happen in the future. The verb form "clouds" is incorrect as the verb after "can" still needs to feature the singular form necessary with the subject "focus." "Can cloud a leader's judgement" is the best choice among the answer.

This sentence will try to trick you into using the subjunctive mood, but remember that the subjunctive is only used to describe hypothetical situations and dreams. Because the character actually did jump into the murky lake, the correct mood is simply the past indicative: “He said he wouldn’t have jumped into the murky lake if someone else hadn’t jumped before him.”

The correct answer choice ("The cheese was given to the child by the parent") uses the active voice instead of the passive voice and makes the most grammatical sense in the sentence. Sometimes the passive voice is necessary, but when it is not necessary, it should be avoided.

The phrase "to correcting" is grammatically incorrect in standard written English, and needs to be "to correct" in the underlined phrase. 

The example sentence expresses a hypothetical condition that is contrary to fact ("I," by definition, am not "you"), and therefore needs to be expressed using verbs in the subjunctive mood. "If" is a usually a good indication that a sentence will be in the subjunctive mood. In the subjunctive, "were" should be used instead of "was." "If I were you, I would leave that job immediately."

This sentence is an example of the present subjunctive, which is most commonly used in English to express hypothetical situations, wishes, and desires. The correct long form of the sentence is “if you were to choose that restaurant,” and “were you to choose that restaurant” is simply an inversion and shortening of the long form. (“Were you to have chosen that restaurant” is the past subjunctive, which doesn’t match the future conditional form of the second half of the sentence.)

The choices that include the pronoun "it" are clearly wrong because there is no noun preceding the word "it" that can be referenced. This question involves a dangling modifier. What is touching on those subjects? The novel. The novel should therefore come after the comma. Eliminate answers that do not have this structure. "Shall" is not usually used in the third person. It is usually used in the first person. It is used to make suggestions or to give offers of help. For example, "shall we go the beach" and "shall I help you with those bags". The sentence is correct as written.

The sentence is correct because we change "was" to "were" following a noun in situations in which the statement communicates something contrary to fact or highly unlikely.

The choices that include the pronoun "it" are clearly wrong because there is no noun preceding the word "it" that can be referenced. This question involves a dangling modifier. What is touching on those subjects? The book. The book should therefore come after the comma. Eliminate answers that do not have this structure. "Must" is clearly awkward. "Shall" is not usually used in the third person. It is usually used in the first person. It is used to make suggestions or to give offers of help, for example, "shall we go to the beach" and "shall I help you with those bags". The correct choice implements the simple structure "the book will tell".