6.I think you've got to the point _________ a change is needed，otherwise you'll fail.
6.C 【解析】where等于in which，修饰the point。
7.After a long discussion， they _________ an agreement.
7.C 【解析】come to an agreement达成协议，是固定搭配。
8.Ellis Haizlip began his stage career in Washington D.C.，_________ supervised the Howard University Players during their summer season.
B.where he was
9.Some people hold that the more conservative the world becomes，_________ have old furniture，old houses and old paintings.
A.the smarter is to
B.the smarter it is to
C.is it the smarter so
D.is one to the smarter
10.She was just about to explain _________ she hadn't passed her maths test chiefly out of carelessness _________ her uncle came.
B.to her mother why;that
C.her mother that;when
D.to her mother that;when
10.D 【解析】explain/announce等后面的结构是～ sth.to sb.或～ to sb.sth.，to 不可省略。