The correct answer is: B. Rs. 90,000
The amount of donation received in 1998 is Rs. 1,00,000 – Rs. 20,000 = Rs. 80,000.
The amount of donation received on 31st December 1998 is Rs. 15,000.
Therefore, the amount of income as donation for year 1998 is Rs. 80,000 – Rs. 15,000 = Rs. 65,000.
Option A is incorrect because it is the total amount of donation received in 1998.
Option C is incorrect because it is the total amount of donation received in 1998 plus the amount of donation received on 31st December 1998.
Option D is incorrect because it is the total amount of donation received in 1998 minus the amount of donation received on 31st December 1998 plus the amount of donation received on 31st December 1997.