The robot b______ to work ay once.
问题描述：
The robot b______ to work ay once.
答
began
答
The robot began____ to work at once【过去式】
The robot begins______ to work ay once【一般现在时第三人称单数要加s】
因为不知道语境,两种填法都可以.
希望对您有所帮助`~