To understand the retrieval sequences in IMS DB, let's go through each option:

A. Top to Bottom - This option is correct because in IMS DB, the retrieval sequence starts from the top level segment and goes down to the child segments. This ensures that the data is retrieved in a hierarchical manner.

B. Front to Back - This option is incorrect because the retrieval sequence in IMS DB is not based on the front-to-back order of segments. It is based on the hierarchy of segments.

C. Right to Left - This option is incorrect because the retrieval sequence in IMS DB is not based on the right-to-left order of segments. It is based on the hierarchy of segments.

D. Left to Right - This option is correct because after traversing down the hierarchy from top to bottom, IMS DB retrieves the segments from left to right within each level. This ensures that the segments at the same level are retrieved in a consistent order.

Therefore, the correct answer is A, B, D. These options represent the retrieval sequences in IMS DB, where the data is retrieved from top to bottom, from front to back, and from left to right.

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