Answer:
A machine have 75% efficiency means 25% of efficiency has been lost due to friction and a machine can work 75% only.
- See charge on ion is -1 .
Hence it has taken 1 electron
Now first look at EC of Fluorine(F)

- Now one electron added .hence no of electrons is 10now
Look at the EC

Or
![\\ \bull\sf\dashrightarrow [He]](https://tex.z-dn.net/?f=%5C%5C%20%5Cbull%5Csf%5Cdashrightarrow%20%5BHe%5D)
Option C is correct.
A catalyst speeds up the rate of reaction so the answer is B.
N₂O₃
3 moles oxgyen atoms in 1 mole .
hope this helps!