When is it acceptable to use the direct write$-$off method to account for uncollectible accounts?

Question $30$ options:

$1)$

When the company pledges its accounts receivables

$2)$

When the expected bad debts are not significant

$3)$

It is never acceptable to use the direct write$-$off method under GAAP

$4)$

When the expected bad debts are significant

$5)$

When the company sells its accounts receivables