circulate的名詞形式

例句：

Draughts help to circulate air.

通風有助於循環空氣。

Leave a gap at the top and bottom so air can circulate.

在頂部和底部各留一點空隙，這樣空氣就可以流通了。

Rumours began to circulate about his financial problems.

有關他財務困難的謠言開始流傳開來。