Ddddddddddddddddddddddddddddddddddddddddd
Option D is the answer because Digital Certificate is an entity that generates electronic and distributes them upon proving their identity sufficiently. In early days there was issues with people using the certificates that were not even issued by the organizations. Today it's a cryptographic technique which uses digital signatures and gives users a digital certificate that can be authenticated anytime online by any organization and is unique for every user having it.
Option A cannot be the answer because it has nothing to do with the identity of person but rather it is for specific fields.
Option B is not answer because it has no key and score matter to do with it.
Option C Web transactions has nothing to do with the certificates.
Answer:

Explanation:
The Hexa-decimal numbers have base 16 and includes numbers:
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F
The given steps are performed to convert a decimal number to hexa-decimal number, here to convert decimal number 35 to hexa-decimal number:
- Divide 35 by 16
- Note the remainder, r which is 3 here and quotient which is 2
- Again divide 2 (quotient) by 16 and note the remainder, r' which is 2 and quotient is 0
- We will stop here as the quotient is now 0. Usually division by 16 is repeated until we get quotient = 0
- Now arrange the remainder in reverse order to get the hexa-decimal number as r'r
- The hexa-decimal number is

Answer:
I would say Alan Turing is the father of the modern computer