concentrated for a long time he____ his work, made some coffee and talked with his colleagues

______was it______ youdiscovered the secret of his—–Totally by chance .

On the top of the hill _________ the old man oncelived.

The form cannot be signed by anyone ________ yourself.(2011·全国Ⅰ)

I have more storybooks than do.— But your books are not as interesting as .