A:being there
B:there having bee
C:there wa
D:should there be
大气中近70%的氧气来源于____。
班固说:“古代天子建国,诸侯立家,从卿大夫到庶人,各有等差。人们尊奉并服侍上级,而在下位的人也不会有逾越的念头。"接着又说:"五霸,三王之罪人也;六国,五霸之罪人也;四豪(信陵君等四君子),又六国之罪人也。"材料反映
It's 6: 30. It's time to g____ up.