I took this question before, and it is A) size in area.
Blocking, covering, obscuring, hiding, concealing, veiling, shrouding, darkening, extinguishing, shading, dimming, declining, diminution, extinction, penumbra
100m runner (don’t mind this i need it to be 20 characters long)
C. It begins with 3/8 and 1/3, and we need to make it 5/8 and 2/3, and the one that does that is C.