In a series circuit with three bulbs,
a. there are many paths for the current to take.
b. the remaining two bulbs are not affected if one bulb burns out.
c. all of the bulbs become dimmer as more bulbs are added.
d. a switch is never used.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

the answer you are looking for is d. there are no holes for blood to enter or leave the system. your welcome