Which of the following is a benefit of using steganalysis techniques in forensic response?

Options:

A Breaking a symmetric cipher used in secure voice communications
B Determining the frequency of unique attacks against DRM-protected media
C Maintaining chain of custody for acquired evidence
D Identifying least significant bit encoding of data in a .wav file    

A small business requires a low-cost approach to theft detection for the audio recordings it produces and sells.

Which of the following techniques will MOST likely meet the business's needs?

Options:

A Performing deep-packet inspection of all digital audio files
B Adding identifying filesystem metadata to the digital audio files
C Implementing steganography
D Purchasing and installing a DRM suite  

NOTE : please don’t share copy/paste publicly available  answer because i have all those open answer with me .. I am doing an analysis here hence correct answer is required

a.A sinewave has a period (duration of one cycle) of 645 μs. What is the corresponding frequency of this sinewave, in kHz, expressed to 3 significant figures? (See Study Note 7.1 in the ‘Using Numbers (maths)’ booklet.)

A (i) If the frequency of the sinewave is now reduced by a factor of 3.5, what will be the new period value? Express your answer in ms, to 3 significant figures.

Note: In the second part of this question, to avoid rounding errors in your calculations, use the full frequency value from the first part, not the rounded value to 3 significant figures.

Which of the following allows computation and analysis of data within a ciphertext without knowledge of the plaintext?

Options:

A Lattice-based cryptography
B Quantum computing
C Asymmetric cryptography
D Homomorphic encryption   Note : someone is saying answer is answer C and other is saying D i am confused ... please help to guide the same