How to identify Double replacement

The easiest way to identify a double displacement reaction is to check to see whether or not the cations exchanged anions with each other.

Explanation:

if the states of matter are cited, is to look for aqueous reactants and the formation of one solid product (since the reaction typically generates a precipitate).

the answer is c

tell me if wrong

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.