9.49am GMT The key challenge is how do European countries tackle globalisation, says Cameron.
Perhaps the key challenge is countering these feelings of cultural (as opposed to just economic) threat.
For countries with a growing working-age population, the key challenge is to generate a large number of productive jobs.
The key challenge is determining what type of alliance Europe wants with the United States going forward.
The key challenge is to balance the academic study and pressures with doing a proper job in the workplace.
The key challenge is to support these five sectors in order to combine short-term relief with long-term reconstruction and development.
The key challenge is to convince young people who are vulnerable to al-Qaida's propaganda that politics can be made – and must be made – to work.
In virtually every robot that's ever been built, the key challenge is generalization, and moving things from the laboratory to the real world.
He said: "If one looks at India or emerging economies, the key challenge is providing basic goods and services to what is known as bottom of the pyramid.
The key challenge is to make effective decisions that avoid vicious spirals while not embracing short-term fixes that fail to address the fundamental issues.
For a presenter the key challenge is not simply to offer the unfamiliar, but also to provide a context in which an audience can approach and appreciate it.
