複選題18.(AB) where (AC) vaulting (AD) yet (AE) project (BC) composed (BD) those (BE) grandeur (CD) reticulated (CE) accretion (BC) which

4. The burst of gamma-ray radiation generated by the mergers of binary star systems are ____ in nature； scientists have found it difficult to collect meaningful data from such a brief of time span. (A) expedient (B) protracted (C) transient (D) sidereal