Задание 3:
2) So
3) Although
4) Because
5) Although
6) So
Задание 4:
2) The train had finally arrived so we have got on it.
3) She felt homesick, although she wasn't away from home for too long.
4) Everyone said the autobiography was amazing, but nobody read it.
5) As soon as we published the book it became a best-seller.
6) Until he spoke i didn't realize he wasn't English.
7) The phone rang when i just fell sleep.
8) I whispered my secret to her when she swore not to tell anyone.