This is a necessary consequence of progress.
这是发展的必然后果。
Repairs are necessary to strengthen the bridge.
这座桥需要加固。
A radical overhaul of the tax system is necessary.
有必要彻底改革税制。
For him, reading was a necessary prelude to sleep.
对他来说,阅读是入睡的必要前奏。
The alliance stands ready to do what is necessary.
该联盟已准备好采取必要行动。