诚实是良好友谊的基石。

Honesty is the ___keystone of a strong friendship.

拱顶的楔形拱心石是这座石拱桥结构稳固的关键。

The wedge-shaped ___keystones at the top are what hold this stone arch bridge together.

信任是任何成功团队的基石。

Trust is one of the ___keystones of any successful team.