precaution可数吗

　　I'll keep the letter as a precaution.

　　我要保存这封信，以防万一。

　　I had taken the precaution of doing a little research before I left London

　　我已在离开伦敦前进行了准备，做了些调查研究。

　　Could he not, just as a precaution, move to a place of safety?

　　就算仅仅是为了以防万一，难道他就不能挪到安全的地方吗？

　　I took the precaution of clearing out my desk before I left.

　　我临走时特地事先把办公桌清理了一下。

　　As a precaution against earthquakes, the building is being reinforced.

　　为了防震，这座楼正在加固。