Under what condition do a feather and an iron ball fall at the same rate ?Explain with reasons. ​

this allows people to make the best decision or pursue the best option. when alternatives are weighed using their advantages and disadvantages, the option whose disadvantages outweigh the advantages (based on a qualitative or quantitative analysis) are shunned while those whose advantages outweigh their disadvantages are pursued.  

a and c

c is 100% but i am confused in a

1/0.14nm = 10^10/1.4 a lot