Option (D) is the correct answer: "The inability of the machine press union and company management to communicate effectively was a major cause of the 1999 strike in Seattle."
This option presents a clear and concise sentence that effectively conveys the intended meaning. The subject of the sentence is "the inability of the machine press union and company management to communicate effectively," and the phrase "was a major cause of the 1999 strike in Seattle" provides important context for the sentence.
Option (A) uses the phrase "it was" as a pronoun to refer back to the subject, which can create confusion about what "it" refers to. Additionally, the use of the phrase "not able to communicate effectively" is less concise than "inability to communicate effectively."
Option (B) changes the sentence structure to "communications between" and removes the subject of the sentence. This can create ambiguity about who or what is being referred to.
Option (C) changes the sentence structure to an infinitive phrase, which creates a wordy and awkward construction. Additionally, the phrase "to be unable to communicate effectively" is less concise than "inability to communicate effectively."
Option (E) changes the sentence structure and omits the subject of the sentence. The phrase "being unable to communicate effectively with company management" creates an awkward construction and does not effectively convey the intended meaning.
Therefore, option (D) is the best answer.