that's a good question—it's one of the best questions i've seen posted here lately. basically, here's the difference: •  "not X but Y" : this construction implies that X is what's "normal" or "expected" , and that Y is what's actually true. e.g., I was surprised to lea...

1. In 1981 children in the United States spent an average of slightly less than two and a half hours a week doing household chores; by 1997 they spent nearly six hours a week. removed "had", the sentence is correct? No. Still wrong. The past tense is incompatible with "by (date)"...