I. Sentence Fill-in : Fill in the blank with the most logically appropriate sentence. 1. ________________ Efforts to develop a vaccine against the brain disorder have stalled, and no drugs have been able to reverse the slow death of neurons that robs people of their memories and thoughts. For the first time in many years, however, researchers in the field are genuinely excited about the potential for effective drug treatments and helpful new risk factors. (A) Alzheimer's disease can be treated by an inexpensive herb called lucerne. (B) Doctors researching on Alzheimer's disease have been optimistic about its treatment options. (C) When it comes to Alzheimer's disease, there hasn't been much to celebrate in recent years. (D) My father is a typical patient of Alzheimer's disease.