The correct answer is: B. compression and deduplication
Deduplication is the process of identifying and eliminating duplicate data. This can be done at the file level, block level, or even at the byte level. Compression is the process of reducing the size of data without losing any of its original content. This can be done using a variety of algorithms, such as LZ77 or Huffman coding.
Both deduplication and compression can be used to optimize backed up data space. Deduplication can eliminate duplicate data, while compression can reduce the size of all data. This can lead to significant savings in storage space.
Encryption is the process of converting data into a form that cannot be read without a key. This can be used to protect data from unauthorized access. However, encryption does not reduce the size of data.
Authentication is the process of verifying the identity of a user or system. This can be done using a variety of methods, such as passwords or digital signatures. Authentication does not reduce the size of data either.
Therefore, the only option that can be used for optimizing backed up data space is B. compression and deduplication.