Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
"The details of the incident was not known."

Assertion (A) :
The above sentence does not adhere to the requirement of subject-verb agreement and hence it is a grammatically incorrect sentence.

Reason (R) :
In "Noun + Preposition + Noun" constructions, the verb agrees with the number and person of the noun preceeding the preposition.
In the light of the above statements, choose the correct answer from the options given below: