The Central Depository performs a fundamental legal and operational function by maintaining the official register of transactions in securities listed on UAE markets. Under the CISI UAE Financial Rules and Regulations, the Depository Centre must keep a register of all transactions involving securities listed on the market. The rule expressly states that any transaction in listed securities that is not registered is deemed null and void . Registration provides the official record needed to establish securities ownership, complete settlement, maintain investor accounts and support rights arising from ownership. A transaction that bypasses this prescribed recording process therefore lacks the regulatory recognition required for a valid market transaction. The other answer choices concern different regulatory obligations or potential misconduct but do not constitute the specific statutory ground for treating the securities transaction itself as null and void. A board member's misconduct, reporting failures or deficiencies in daily monitoring may lead to separate enforcement or governance consequences. The direct trigger tested here is failure to record the transaction according to applicable regulatory provisions. Therefore, option A is correct.