The correct spelling of the phrase "was mark" is /wɒz mɑːk/. The first word "was" is spelled with a single "s" despite the pronunciation being /wɒz/ because it is a past tense form of the verb "be". The second word "mark" is spelled with a "k" at the end to differentiate it from the similar-sounding word "mar", which has a softer ending. It is important to pay attention to phonetic pronunciation when spelling words to avoid confusion or miscommunication.