【正确答案】 C

【答案解析】[理由] 本句测试下列结构：
so+adj/adv+that引导的状语从句
如此地……以致于……
such+名词+that引导的状语从句
如此地……以致于……
[例] I was so excited(形容词) that I couldn't fall asleep last night.
(我太兴奋了以致于昨晚睡不着觉。)
It is such a big house(名词) that it takes a lot of effort to keep it clean.
(这栋房子很大，所以要保持清洁得花费许多心力。)
根据上述，空格前有so good(如此地好)，得知空格内应置连接词that引导的状语从句，合乎语意及用法，故(C)应为正选。
(D)项的therefore虽表“因此”，但本字是副词，在句中使用时之前应置分号，以连接两句。
[例] Business has been very good over the last two seasons; therefore, the general manager has promised to take all the staff on a trip to Europe in early July.
(上两季的生意非常好，因此，总经理答应在7月初带全体员工去欧洲旅行。)