spread是哪個(gè)單詞的過(guò)去式

　　Prompt action was required as the fire spread.

　　由于火勢(shì)蔓延，須要立即采取行動(dòng)。

　　The clouds had spread and covered the entire sky.

　　烏云鋪開(kāi)，遮蔽了整個(gè)天空。

　　Fire spread rapidly after a chemical truck exploded.

　　一輛裝有化學(xué)品的卡車爆炸后火勢(shì)迅速蔓延開(kāi)來(lái)。