(B) since these families can no longer afford to buy homes, furthermore
感觉since做连词有问题：
1.如果做“自从.....以来”解释的话，似乎因果关系上有问题，应该是gap widens造成families can no longer afford to buy homes。而不是自从families can no longer afford to buy homes以来gap widen
2.做“原因”解释的话，也说不通
furthermore是副词，不是连词不能通过“逗号+副词+句子”来连接两个句子吧，而yet可以是副词也可以是连词，可以连接句子 | 
