In order to correct sentence 7, you should change \u201Cplay\u201D to \u201Cplays.\u201D The subject of the verb \u201Cplay\u201D is \u201CTransportation,\u201D which is singular and requires the use of a singular verb; therefore, you should use \u201Cplays\u201D instead of \u201Cplay.\u201D As a rule, \u201Can\u201D should only be used before words that start with a vowel (i.e. a, e, i, o, and u) or before a word that contains an unpronounced \u201Ch\u201D (i.e. hour). Therefore, \u201Ca\u201D should be used before words that begin with a consonant (i.e. b, c, d, f, ...). In this sentence, the \u201Ca\u201D and \u201Can\u201D are used correctly. As a rule, you would use \u201Cwho\u201D to refer to a subject (\u201Csuburban resident\u201D) of a clause and \u201Cwhom\u201D to refer to an object of a clause. In this sentence, \u201Cwho\u201D is used appropriately.