教甄◆英文科題庫下載題庫

After the UFO sightings and the Roswell incident of 1947, U.S. Air Force General Nathan Twining undertook a study of the strange objects that were seemingly ___40_____ through the skies. This study group was given the code name Project Sign. Project Sign studied 147 cases; 135 cases could be explained, but 12 could not. The group decided that those 12 sightings were actually of ___41_____ from another planet. Air Force Chief of Staff General Vandenberg rejected the report. He said that the evidence gathered did not support such an astounding conclusion. Vandenberg’s rejection ruined ___42_____ at Project Sign, and the case officers were soon merely collecting and filing reports, and did very little investigative work. They felt they had done their best and that the brass had rejected it. 

In 1949, Project Sign became Project Grudge. Project Grudge took a different approach. The researchers opted to try to explain every UFO report no matter how fragmentary. In 1952, Project Grudge went public and was renamed Project Blue Book. However, after 12 years of investigation, the project found no compelling evidence that UFOs were either ____43____. or a threat to national security.