begin 的过去式和过去分词是什么

Work has begun on the construction of the new airport.

新机场的修建已经开工。

The firm has begun a major push into the European market.

这家公司已展开了对欧洲市场的重要攻势。

It was tough talk, coming from a man who had begun the year in a hospital bed.

这话出自年初住进医院的一位男子之口，语气很强硬。

He began by making a few general observations about the report.

开头他先对这个报告作了几点概括性的评论。

Slowly, an image began to appear on the screen.

屏幕上慢慢地出现了一幅图像。