It contained all the necessary information about the moon and stars that sailors would need to help them learn their longitude.

VOA: special.2010.07.14

Why don't bacteria need a distinct nucleus and that's necessary in a human cell?

为什么细菌不需要单独的细胞核,而对人类细胞则为必需

耶鲁公开课 - 生物医学工程探索课程节选

"The lack of access is also affecting the ability of the Afghan population to obtain the necessary medical assistance and basic services, which they need,and which they are increasingly not getting,"

VOA: standard.2009.08.07

The G-20 was set up as an ad hoc response to the financial crises of the 1990s to meet the need to expand necessary international financial and economic cooperation beyond the seven largest economies plus Russia to include developing nations, like China, India and Brazil.

FORBES: G-8 + G-20 = G-20

Some of the changes that are necessary need to take place, and the important steps that have to be demonstrated and the constitutional change that we need to see, that the people of Egypt need to see, on the road to free and fair elections.

WHITEHOUSE: Press Briefing

You also need procedures to implement the plan should it become necessary, and you need to revise the plan as your business changes.

FORBES: Disaster Recovery in the Cloud