Read the excerpts from "one flu over the cuckoo's nest." scientists debated creating a killer virus to study in the lab. in 2005, the centers for disease control proposed deliberately combining a deadly bird flu virus with a very contagious human flu virus to understand whether and how it might cause a worldwide outbreak, or "pandemic." scientists said the lab experiments would them understand what might already be happening naturally. the proposed experiment was highly controversial. *** but other people thought such research was a terrible idea. what if these viruses escaped the lab by mistake? what if a government or terrorist organization wanted to use the viruses against their enemies? which phrase creates a fearful tone in the excerpt? a. the lab experiments would them understand b. proposed experiment was highly controversial c. the centers for disease control proposed deliberately combining d. a government or terrorist organization wanted to use the viruses