Although he was weak,still he tried his best to do the work.
虽然他很弱,他仍然尽他最大的努力去工作.请采纳。谢谢！A.but B./C.andD.or选BAlthough he was weak, he tried his best to do the work. 已经是一个完整的句子，再添加but, 就是画蛇添足。