World player of the year Cristiano Ronaldo answered his skeptics, including manager Alex Ferguson, with a career-best goal that sent defending champion Manchester United into the Champions League semifinals yesterday.

Ronaldo’s spectacular long-range strike provided a 1-0 victory over FC Porto and a 3-2 aggregate score in the quarter-final series.

“It is the best I have scored,” Ronaldo said. “It was a fantastic strike and I can’t wait to see it again on DVD. I am very happy with it.”

The Portugal forward began his run from inside the Porto half in the sixth minute and sent a rising shot from 40 yards past diving goalkeeper Helton into the top corner for only his second goal of the competition.

The goal came only days after Ferguson scolded the young winger for a turnover that led to Porto’s opening goal in the 2-2 first-leg draw at Old Trafford. Yesterday, Ferguson was just as stunned as the 45,000 fans at the Stadium of Dragon.

“Unbelievable,” Ferguson said. “A magnificent hit, absolutely unbelievable ... the goalkeeper’s got no chance.

In other action, Arsenal romped into the semifinals to face Man U with a 3-0 defeat of Villarreal to seal a 4-1 aggregate victory.

Theo Walcott set the tone with an early opener before Emmanuel Adebayor’s goal and a Robin van Persie penalty finished off Villarreal.