RiyaGangar
Numbers are chosen without replacement. If sum is 14, one of the numbers cannot be 7 since 7 can be chosen only once. Therefore sum of other 2 numbers is 14. Total sum = 7+14=21. Hence B is sufficient.
Thank you so Kuch Riya for this. Much grateful

HarshR9
One of the 3 numbers picked is 7. Let the other two be "a" and "b".
(1) sum of two of the numbers is 16. Here, there are several possibilities.
For instance,
(7,9,2). 7+9 = 16. Overall sum is 18.
(7,9,5). 7+9 = 16. Overall sum is 21
(7,10,6). 10+6 = 16. Overall sum is 23.
Clearly Statement 1 is not sufficient.
(2) The sum of two of the numbers chosen is 14.
Here, we can be sure that 7 is not one of the 2 numbers whose sum is 14. Because for 7 + some number to give 14, the other number has to be 7 again. But we are drawing numbers without replacement. 7 again is not possible.
Hence, the sum of the OTHER TWO numbers (excluding the 7) is 14. a+b = 14
Then, the overall sum is (a+b+7) = 14+7 =21.
Hope this helps!
Harsha
Finally understood. Just the explanation I was looking for.
Thank you very very much Harsh. God bless.