This means their children will for sure have the family disease, ____ , as a matter of fact, is a great trouble for these families. 填meanwhile对不对?若不对答案是什么?
不对呀，应该填which，因为这里as a matter of fact是插入语，事实是……，如果把这个短语去掉，就是This means their children will for sure have the family disease， is a great trouble for these families. 这里显然是定语从句缺少一个引导词，而且这个引导词在定语从句里要做主语，所以应该填which，而不应该填连词。
cherry回答的是对的，我再补充一点，即便把as a matter of fact这个插入语去掉，也应该填which，因为as a matter of fact前有逗号，这是非限制性定语从句的标志，只能用which。而且又有了as a matter of fact这个插入语，有插入语的定语从句，加的一定是which