The to the rocket going into space went wrong, and as a result it exploded and fell into the sea.
A. mark
B. sign
C. symbol
D. signal
网友回答
A. mark
B. sign
C. symbol
(答案→)D. signal
解析：A．mark记号，B．sign迹象，标志，C．symbol象征，D．signal信号，句意：进入太空的火箭信号出了问题，因此它爆炸了掉入海里。根据句意选D。