III. Cloze Test (40%) Passage 1: Questions 21-25 The James Webb Space Telescope — humanity's biggest __(21)__ yet in its quest to probe the Universe — soared into space on 25 December, marking the culmination of decades of work by astronomers around the world. But for Webb to begin a new era in astronomy, as many scientists hope it __(22)__, hundreds of complex engineering steps will have to go off without a hitch in the coming days and weeks. "Now the hard part starts," says John Grunsfeld, an astrophysicist and former astronaut and __(23)__ of science for NASA. The US$10-billion Webb is the most complicated and expensive space observatory in history, and the __(24)__ to NASA's Hubble Space Telescope, which has studied the Universe since 1990. Following its launch, Webb will now embark on the riskiest part of its mission — __(25)__ all the parts required for its enormous mirror to peer deep into the cosmos, back towards the dawn of time. 21.