Answer: Option A) De facto standard
Non proprietary standard is also termed as de facto standard.
Explanation: Non proprietary standard is also termed as de facto as when the proprietary standard such as window are widely used, then it becomes de facto standard. When de facto standard is referring in terms of computers, it is an accepted application, design or language standard that is used in industry but not officially recognized.
An example of de facto standard is paper clip ion used in e-mail to represent an attachment.
