Assertion (A): The Supreme Court is a court of record.
Reason (R): It delivers judgment in open court.

The correct option is A Both A and R are true and R is not the correct explanation of A.
Correct reason or explanation would have been- "All the acts and proceedings of Supreme Court are kept on permanent record"
Supreme Court is a ‘Court of Record’. This means that all judgements and orders made in the court are carefully recorded. The judgements can be produced in any court as ‘precedents’. These are cited as an example to justify deciding a similar case in the same manner. Precedents act as guidelines for future verdicts. If a High court is faced with a case which has similar facts to one handled by the Supreme Court, it can take a look at the record.

And also The Supreme Court delivers judgments in open court to ensure that justice is done. Judgments are usually pronounced immediately after arguments conclude, or on a later date with notice given to the parties.