The change in net working capital in 2021 is $7. The Option D is correct.
The change in net working capital refers to the difference between a company's current assets and current liabilities between two accounting periods.
Change in net working capital in 2021 = ((Cash of 2021 + Other Current Assets of 2021) - (Cash of 2020 + Other Current Assets of 2020)) _ (Accounts Payable of 2021 - Accounts Payable of 2020)
= ($69 + $174) - ($57 + $167) - ($129 - $117)
= $7
Therefore, the change in net working capital in 2021 is $7.