7. An example of an element is
A. Air
B. Iron
C. Sugar
D. Water

it’s previous models   because when i picked that son of a gun’s answer it was wrong look for previous models because they might make it a different letter  

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.

the answers are

c and c