Boris Johnson said today he could not go on "endlessly dodging" questions about his future.
But the Mayor of London played down his chances of success, saying it was "highly likely" he would fail to find a suitable constituency in which to run.
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Mr Kim has made two recent visits to China.
The study looked at the development of 422 children over the course of eight years.
The president said they will come into force if China refuses to change its practices.