Answer: C. April 15, 2020.
Step-by-step explanation:
If Karen hopes to receive a refund on the amended 2016 return then she should file it within 3 years of the day she filed her 2016 return.
She filed her 2016 return on April 15, 2017 so three years from then would be:
= 2017 + 3
= 2020
April 15, 2020