Answer:
Existence or Occurrence
Explanation:
Based on the information provided within the question it seems that Nick is concerned about the Existence or Occurrence of the inventory balance. This is an assertion that tries to verify if certain assets exist and if the transactions that have been recorded actually happened. Since Nick believes that the inventory balance increase seems suspicious he is concerned that there may be fraud or a mistake in the records, therefore he may have to go to the inventory and check for himself.
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