Italy sold another bundle of government debt Thursday at levels well below the last bond auction. But the political pressure on the government of Prime Minister Mario Monti remained high - and was rising. Despite a dramatic drop in short-term borrowing costs Wednesday, the continuing high yields on the benchmark 10-year bonds - just shy of the psychologically important 7 percent rate - pointed to continuing challenges ahead. Italy, the eurozone’s third-largest economy, must refinance almost 200 billion euros in government debt by April, and if borrowing rates remain high, the country could face a solvency crisis that could threaten the stability of the euro.