The correct option is C 2×10−4/∘C
Since on heating the length of the wire increases, it expands outwards, making the size of the ring bigger. consequently, the gap in the ring also becomes bigger in the same proportion.
So, if 1 cm become 1.02 cm, 60 cm will become 61.2 cm
So, change in length =61.2 cm −60 cm = 1.2 cm
original length is 60 cm and change in temperature = 1000 C
Putting these values in the formula of α=dll×dt, where dl= Change in length and dt= change in temperature, we get, α=2×10−4/∘ C