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Solution

Cipher Feedback Mode is a block cipher mode that converts a block cipher into a stream cipher.

It is called self synchronizing because if some bits are lost or damaged, the system can automatically resynchronize after some blocks.

Output Feedback Mode is also used like a stream cipher, but it is a synchronous stream cipher, not self synchronizing.

Electronic Codebook Mode encrypts each block independently.

Cipher Block Chaining Mode uses the previous ciphertext block for chaining.

Therefore, the block cipher mode used as a self synchronizing stream cipher is Cipher Feedback Mode.