Which country attacked the twin towers?

Answer 1

The Twin Towers were not attacked by a specific country. It was attacked by a group of extremists that were (and still are) unhappy with the United States' involvement in Middle Eastern affairs.

Although the identities of the hijackers are known, the exact method of their recruitment and training will likely never be discovered. They spent months to years in the US and some learned English to attend various flight schools. The 19 hijackers were mostly Saudi, but included one each from Egypt, Lebanon, and the United Arab Emirates.