她走得太快了，我跟不上她。

She was walking so fast I couldn't ___keep ___up ___with her.

不幸的是，他太快了，我无法跟上他。

Unfortunately he was too fast and I couldn't ___keep ___up ___with him.

在马拉松比赛中，许多跑者觉得很难跟上节奏。

During the marathon, many runners find it hard to ___keep ___up ___with the pace.