Which of the following best simplifies sentence (4)?

Directions for the question:

The following passage is an early draft of an essay. Some parts of the passage need to be rewritten. Read the passage and select the best answer for the question that follows. Keep in mind that some questions are about particular sentences or parts of sentences and ask you to improve sentence structure or word choice. Other questions ask to consider organization and development. In choosing the answer, follow the requirements of standard written English.

(1) In a world growing ever more noisy, a fight of vital importance to us all is under way – against the tyranny of noise. (2) Noise frays the nerves, lessens efficiency and robs us of sleep. (3) The old and infirm cannot sleep, the student cannot read, the sage cannot meditate, and the professional cannot concentrate. (4) If the general noisy condition of everyday life continues, it is not inconceivable that we might become a race of shouting maniacs. (5) To primitive man, noise was nature’s warning of approaching danger and his response was automatic. (6) The roar of a lion sounds the alert and the human nervous system takes over preparing the man for fight or flight. (7) Today we respond exactly as the primitive man did. (8) An explosion occurs and we are startled. (9) A loud noise and the new-born baby reacts with wide-eyed fear, clutching. (10) Unnecessary noise subjects us to countless false alarms daily and keeps us almost continuously alert. 

(11) Many doctors believe that there is a direct link between this unconscious tension and the rise of such stress conditions as heart disease, hypertension and other disorders. (12) Noise causes the mind to ‘blink’ – split–second periods of blanking. (13) This effect, combined with the annoyance, can lessen efficiency, lower production and make people more error–prone.