问题补充：
they are twin brothers, they don’t look like each other.
A. Though
B. Since
C. However
D. When
答案：
A. Though
B. Since
C. However
D. When
解析：考查连词辨析。A. Though虽然； B. Since自从，因为；C. However然而； D. When当。。时候。句意：虽然他们是双胞胎兄弟，但他们一点也不象。根据下方提到they don’t look like each other可知，选A项。
考点 :考查连词辨析
