Answer: (b)
Step-by-step explanation:
Given
R is inversely proportional to A i.e
[tex]R\propto \dfrac{1}{A}\\\\R=\dfrac{C}{A}\quad [\text{C=Constant}][/tex]
when [tex]R=4,\ A=100[/tex]
Insert the values to get C
[tex]\Rightarrow 4=\dfrac{C}{100}\\\\\Rightarrow C=400[/tex]
When A=250
[tex]\Rightarrow R=\dfrac{400}{250}\\\\\Rightarrow R=1.6[/tex]
option (b) is correct