The error lies in part R of the question. Therefore, the correct answer is option 3. Distributive Pronouns refer to persons or things one at a time. Examples of such pronouns are either, neither, each - these words indicate how something is shared or divided among the members of the group. They are always singular and are hence followed by the verb in its singular form. In the given sentence, ‘either of these roads’ means one or the other road. So, the verb ‘lead’ should be used in its singular form in the present tense. Correct sentence - According to the GPS-aided map, either of these roads leads to the airport. Note – When the two elements being referred to in the sentence “Either element A or element B” are singular, the verb followed is also singular. If both the elements are plural, then the verb followed is plural. Examples: Either Ramesh or Suresh is going to the mall. Either the dogs or the cats are making noise.