Completed in 1891, in what was known as the Gilded Age , the building
is now owned by a famous writer .问:这是道语法填空题,in what was known as the
Gilded Age此句中in后要填what,说是引导宾语从句,且在从句中作主语,我怎么看不出来是如何作的宾语从句...
And last year Khan Academy and the College Board unveiled a free course they say boosts SAT scores for students at all income levels.这里的黑体部分是插入语吗,如果是为什么没有逗号呢?如果不是那是什么成分?