occur

1. V-I When something occurs, it happens. 發生

If headaches only occur at night, lack of fresh air and oxygen is often the cause. 如果頭痛衹發生在晚上，缺少新鮮空氣和氧氣常常是其原因。

The crash occurred when the crew shut down the wrong engine. 機組人員關錯發動機後就墜燬了。

2. V-I When something occurs in a particular place, it exists or is present there. (某事物在某地) 出現

These snails do not occur on low-lying coral islands. 這些蝸牛不會出現在低窪的珊瑚島上。

3. V-I If a thought or idea occurs to you, you suddenly think of it or realize it. (想法、主意在某人腦海中) 突然出現[no passive, no cont]

It did not occur to me to check my insurance policy. 我沒想到要核對我的保險單。