London mayor Boris Johnson has rejected the call for an election pact between Conservatives and the UK Independence Party (UKIP), declaring that voters have "had enough" of pacts and coalitions.
He added: "What they [voters] want is to see parties standing up individually for what they believe in."
More top news
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.