他上周刚签约加入了一家科技公司。

He just ___signed on with a tech company last week.

广播电台通常在早上5点开始播音。

The radio station starts ___signing on at 5 AM every morning.

失业后，她不得不去就业中心登记领取救济金。

After losing her job, she had to go ___sign on at the employment center to claim benefits.