sprout的过去式怎么变化

　　例句：

　　The seeds will sprout in a few days.

　　这些种子几天后就会发芽。

　　New businesses are also sprouting.

　　新的致富门路也在不断出现。

　　Even in frost roots are usually unharmed and they produce new sprouts.

　　即使在霜冻期根部一般也不会受损，而且能萌生出新芽来。