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。