A is wrong.
B is correct.
C is true but magnetic monopoles have been predicted in theory, but never found in practice.
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:
Follows are the matching to this question:

Explanation:
While time-consuming or prone to errors mechanical adjustments to both the referential, databases could be configured with four measures to engine violations. The restricted action causes the insert, update, and removes to only be denied. Set Null to NULL sets the invalid external key, whereas Set Default to a specific core consideration specified in SQL sets a default foreign key. Its Cascade operation spreads the main changes in external keys.
The issue arises because the string you are trying to print is not a string, rather a float value. Item1, item2 and item3 are strong values (if you type some alphabets in it and not just numbers), but itemonecost, itemtwocost, and itemthreecost are explicitly type casted to float. In line 22, 23, and 24 you’re trying to print a float, by adding it with the string. One cannot add numbers to string. Rather you can type cast the itemcost to string while printing.
Add str(itemonecost) instead of itemonecost in print statement. Do this for other float variables too.
However do note that there are multiple ways to correct this issue, and I’ve just pointed one out.