The really difficult question for the religions to answer who claim a sole handle on "The Truth", as do Mormons, and of course the WT/JW brand, is :
"When did "the truth" (the brand or religion) become the "Truth" ?
When they were teaching error, it could not have been "The Truth" , so the subsequent question "How can you be sure it is now ?" is a bit of aposer for 'em !