sign them
The most common reason is a faulty flasher unit.
Assuming that "exam" refers to a school test, most would see the failure negative since most religions approve of education. However, if the exam were in a subject antithetical to the religion, a religion might see the failure positively because you were unable to be disuaded from the "proper" thought-path.
The most common reason for graft failure is the formation of a hematoma, or collection of blood in the injured tissues.
Sadly, I think the most common reason for picking a political party is "Because that's what my parents were".
Speeding, tailgating, running a red light, failing to yield, over correcting, and failing to wear a seat belt.
Drivers, sometimes installation.
An unstable system Incorrect installation Software conflicts
The most common reason is not compatible drivers. In rare cases you can get failing hardware. You need to write down those numbers which you see on the blue screen and google it.
cheating
Obesity.
The most common reason for failure to obtain federal assistance is lack of adequate documentation.