I'm pretty sure it's (A) Fused Sentence
B. more than two things.
C. two people or three items.
D. one thing to another.
I was very frightened while the stranger was knocking on my door.
I was, very frightened, while the stranger was knocking on my door.
I was very frightened, while the stranger, was knocking on my door.
If that is your IQ, then you are extremely, EXTREMELY average. Congrats on being super average, dude.