he is very young he knows a lot about how to be healthy.A. Though; butB. Although; butC

问题补充：

he is very young, he knows a lot about how to be healthy.

A. Though; but

B. Although; but

C. /;but

D. Although;/

答案：

A. Though; but

B. Although; but

C. /;but

(答案→)D. Although;/

解析：句意：虽然他非常年轻，但是他知道很多如何保持健康的知识。Although/ Though尽管，不能与but连用，故选D