单选题 The gap between those at the lowest level and those at the highest level of income has increased ______, and is coming to increase.

【正确答案】 A

【答案解析】解析：句意：最高收入者和最低收入者之间的收入差距已经大幅增长，而且仍在增加。substantially“实质上地，大体上地”；successfully“成功地，顺利地”；succinctly“简洁地，简便地”；sufficiently“充分地，足够地”。根据句意，本题答案为A。