ANS:D - becoming more common

1. It is not necessary for a user friendly system to be object oriented, as we have made programs in c++ which are sometimes not user friendly.

2. User friendly systems are not always easy to develop. While developing such system we must have to consider the system from all kinds of users point of view. The ease with which they can use a sytem. So it is offcourse not an easy task.

3. Traditional mainframe os are developed by experts and they are generally used by experts or scientist.

Only. It was not used by common users as it wasvery complex for them. So mainframes are not user friendly.

But. Userfriendly systems are becoming common because today main moto while developing an application is that only. How user friendly it is.