"His son was present by phone during the meeting"



Which one is correct?



A is correct. This is the pronunciation used for the adjective and noun.

Pronunciation B is never used for the normal word "present". It could only be used for "pre-sent", meaning sent previously, but "pre-sent" is unusual at best.

The other regular pronunciation of the word "present" is "priZENT", with the stress on the second syllable. This is used for the verb.