... the same form: The topology course was both rigorous and challenging. 128 Vocabulary 4000 • When a series of clauses is listed, the verbs in each clause must have the same form. Example: During ... brewing in Europe, the industrial revolution well-established, and a nascent communication age. (A) war brewing in Europe, the industrial revolution well-established, and a nascent communication age. ... war in Europe, the industrial revolution well-established, and a nascent communication age. (D) war brewing in Europe, the industrial revolution well-established, and the communication age beginning....