keep的过去式是什么

He kept us at it all day.

他让我们不停地干了一天。

For reasons of security the door is always kept locked.

为了保证安全，门总是锁着的。

Dogs must be kept on a lead in the park.

狗在公园里必须系着牵狗带。

The bills kept coming in, one after another.

账单纷至沓来。

Next year's collection is still being kept under wraps.

明年的时装系列仍在保密之中。