The correct option is B 4 ohm
We know that RT=Ro(1+αT) where RT= resistance at temp T,
Ro= resistance at 0∘C
α= temperature coefficient of resistance.
5=Ro[1+50 α].....(1)
and
6=Ro[1+100 α].....(2)
Dividing (1) by (2),
56=1+50 α1+100 α
⇒6+300 α=5+500 α
or 1=200 α
or α=1200
From Eq. (1),
5=Ro[1+50×1200]
or 5=Ro[1+14]
or Ro=5×45 Ω=4 Ohm