却是

He´s the best teacher, even though he has the least experience.

他虽然经验最少，却是最出色的老师。

He shouted after them, vainly trying to attract their attention.

他在他们的后面高喊，想引起他们的注意，却是徒劳。

I thought my answer was correct, but it was erroneous.

我原以为我的答案是对的， 可结果却是错的。

Although she was wealthy, she lived in an unpretentious house.

她虽然富有， 住的却是朴素的房子。

He´s keen, but his youth is a minus factor.

他非常精明， 但他的年轻却是个不利的因素。