China's economic growth slowed to a three-year low in the fourth quarter as domestic demand softened, and while the full-year pace hit Beijing's target, trade tensions and structural imbalances pose significant risks to the outlook. China's economy grew 4.5% in the fourth quarter from a year earlier, data from the National Bureau of Statistics (NBS) showed on Monday, slowing from the third-quarter's 4.8% pace as consumption and investment dragged.