Hi Kurshaad,
Thank you for reaching out. For Question 11, if you have a look at the left and right sides of the object, you will notice that both sides are slanted. Hence, option D is the correct answer. The more practice you get in, the easier it will become to visualize these objects.
Here is an introductory video on Keyholes:
https://www.youtube.com/watch?v=_P7IC2z6zM0