When is an original work generally considered to be in the public domain?

Responses

if the creator obtained a specific license for the work
if the creator obtained a specific license for the work - no response given

if the creator is alive and at least 70 years old
if the creator is alive and at least 70 years old - no response given

if the creator has been dead for at least 70 years
if the creator has been dead for at least 70 years - no response given

if the creator makes it available for all to use

if the creator makes it available for all to use - no response given