Choice "A" is correct. Allowance for uncollectible accounts:

Thus, the expense (?) equals $11,000. Note that $350,000 accounts receivable less the allowance for uncollectible accounts balance equals the $325,000 net accounts receivable.Choice "c" is incorrect. Uncollectible accounts expense is not defined as the difference between the beginning balance in the allowance for uncollectible account and the ending balance without regard for transactions during the year.
Choice "d" is incorrect. The allowance account should be credited for the $2,000 written off accounts now collectible.
Choice "b" is incorrect. The allowance account should be credited for the $2,000 written off accounts now collectible, and debited for the $18,000 uncollectible accounts written off.