The correct answer is A. Rs. 20.
The value of a right is the difference between the market value of the share and the right issue price. In this case, the market value of the share is Rs. 200 and the right issue price is Rs. 180, so the value of a right is Rs. 20.
Option B is incorrect because it is the right issue price. Option C is incorrect because it is the market value of the share. Option D is incorrect because it is twice the value of a right.