he is good at playing basketball he failed to join the school basketball team yesterday.A

问题补充：

he is good at playing basketball, he failed to join the school basketball team yesterday.

A. Since

B. Unless

C. Though

D. Because

答案：

A. Since

B. Unless

C. Though

D. Because

解析：连词辨析。A自从，既然；B除非；C尽管；D因为；尽管他擅长与打篮球，昨天他却没有能参加校篮球队。故C正确。