Answer :
C) 2N/M
The formula is F=ke
where F = force,k= spring constant and e=elasticity
2=k*1
k=(2/1)
k=2N/M
- Force=2N=F
- Stretched=x=1m
We know
[tex]\boxed{\sf Spring\:constant(k)=\dfrac{F}{x}}[/tex]
[tex]\\ \sf\longmapsto k=\dfrac{2}{1}[/tex]
[tex]\\ \sf\longmapsto k=2N/m[/tex]