填空题 Questions 18-22
Complete the summary using the list of words, A-N, below.
Write the correct letter, A-N, in boxes 18-22 on your answer sheet.
(18) the formation of black holes requires huge mass of stars, while smaller stars can only (19) or expand. However, based on the calculation of Dr Clark's team, although the magnetar-begetting star of Westerlund 1 was met the requirement of (20) , it was not a black hole, which was not fully astrophysically solved. Lucio Mayer with his colleagues (21) the merge which (22) occurred between massive protogalaxies in early universe, and they have obtained results which satisfied the observed dat

• a.
  A. Simulated B. Experimentally C. collapse D. merge E. Theoretically
  F. windle away G. obviously H. mass L volume J. calculated
  K. normally L. occasionally M. concluded N. precisely