When should you question a sources credibility? ? a. when you cannot find any other sources that support its argumentsb. when the arguments made by the author of the source are consistent  c. when the source has been translated from another language  d. when you find multiple additional sources that support its arguments 

the lachish letters were written by hoshaiah, a military officer stationed possibly in mareshah,   and sent to yaush, possibly the commanding officer at lachish.

the series of letters were written in carbon ink in ancient hebrew on clay ostraca, shortly before lachish fell to the babylonian army of king nebuchadnezzar in 588/6 bc during the reign of zedekiah, king of judah.