Explanation:

- The incident of throwing a bomb at Viceroy Lord Hardinge in Delhi happened in 1912.

- The correct organisation responsible was the Yugantar group (Option:3). Yugantar was a revolutionary group in Bengal closely involved in such activities.

- Anushilan Samiti (Option:1) was also a revolutionary organisation from Bengal and did engage in similar activities, but the specific act against Lord Hardinge was attributed to Yugantar.

- All India Labour Association (Option:2) was a workers' association and not known for revolutionary violence.

- United Patriotic Association (Option:4) was not associated with revolutionary acts or bombings.

Correct Answer: Option:3, Yugantar