等边三角形绕着它的中心至少旋转( )度后能与自身重合.
120
Yesterday I went to see him, _________ that he had gone abroad two days before.
A.only to learn
B.to learn only
C.only learned
D.only learning
停窑后应一次风机运行()小时,再开事故风机运行4时,以冷却保护燃烧器。