It suddenly begin to rain, to my delight, I took an umbrella.

忽然下雨了，令我高兴的是，我带了伞。（这是翻译）

youdao

Under some conditions, algae suddenly begin to spread very quickly, an event known as a bloom.

一定条件下，藻类突然开始迅速繁蔓，这一事件被称为爆繁。

youdao

If you suddenly begin gushing about how GREAT the interviewer's haircut is, the interviewer will see right through your charade.

如果你突然大谈特谈面试官的发型多么好，面试官马上就能看穿你的小心思。

youdao

And then suddenly things begin to change.

事情突然开始发生变化。

哈佛公开课 - 幸福课课程节选

For people whose hearts sometimes suddenly begin racing, having one of these things in your chest is like having an ambulance crew a few inches away.

FORBES: Bad medicine

They say with President Bush well into his second term and facing strong opposition on Iraq there's little incentive for Iraq's insurgents to suddenly begin cooperating with either the American-backed government in Baghdad or the Sunni neighbors.

NPR: Rice, Syrian Official Discuss Porous Iraq Border

He was surprised himself when, in 1983, Begin suddenly left political life and he became prime minister.

ECONOMIST: Yitzhak Shamir