To answer this question, the user needs to have a basic understanding of what a data layer is and its responsibilities.

The data layer is an abstraction layer between the application and the database. Its primary responsibilities include retrieving, updating, and deleting data in the database.

Now let's go through each option:

A. Retrieving information from a database: This is one of the primary responsibilities of a data layer. It retrieves data from the database and provides it to the application layer.

B. Updating information in a database: This is also one of the primary responsibilities of a data layer. It updates data in the database based on the application's requests.

C. Deleting information in a database: This is also a responsibility of a data layer. It deletes data from the database based on the application's requests.

D. Both a and b: This option is partially correct. Option A and B are both responsibilities of a data layer. However, deleting data is also a responsibility of a data layer, making this option incorrect.

E. All of the above: This option is correct. All three responsibilities mentioned in options A, B, and C are responsibilities of a data layer.

Therefore, the answer is: E. All of the above.