In order to correct sentence 17, you should change \u201Cexcursion\u201D to \u201CExcursion.\u201D In this sentence \u201Cexcursion\u201D is being used as a proper name of a vehicle; therefore, it should be written as \u201CExcursion.\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 is used correctly. By using \u201Cwas\u201D the sentence shows that it is in the past tense; therefore, the verb \u201Cdesigned\u201D needs to remain in the past tense. The word \u201Ccollision\u201D is used appropriately in the sentence and should not be changed.