The correct option is A 197 and 198
197 and 198 are both close to 200.
Thus, the sum 197+198 is best estimated by the sum 200+200=400, which is greater than 300.
But, the sum of 101 and 99 is best estimated by 100+100=200, which is less than 300.
The sum of 137 and 133 can be estimated by 100+100=200, less than 300.
Similarly, the sum 126+127 is estimated by 100+100=200, which is less than 300.