To solve this question, the user needs to have knowledge about the PeopleSoft HR system and the different occurrence levels.

Each record in PeopleSoft HR system has an occurrence level, which determines how many effective-dated records a single employee can have for that record. The EFFDT field is a key field that determines the effective date of the record.

Now, let's go through each option and explain why it is right or wrong:

A. 0: This option is correct. Occurrence level 0 is a special level used for control tables that cannot have effective-dated records. Therefore, the EFFDT field cannot occur at level 0.

B. 1: This option is incorrect. Occurrence level 1 is used for records that can have only one effective-dated record per employee. The EFFDT field can occur at level 1.

C. 2: This option is incorrect. Occurrence level 2 is used for records that can have multiple effective-dated records per employee but are not related to job data. The EFFDT field can occur at level 2.

D. 3: This option is incorrect. Occurrence level 3 is used for records that can have multiple, related effective-dated records per employee. The EFFDT field can occur at level 3.

Therefore, the correct answer is:

The Answer is: A. 0