Definition: Given the Question and Answer pair, detect whether the answer is acceptable or not. Denote acceptable answer as "yes", otherwise denote as "no". An acceptable answer is consistent with the context in question, detailed, long, and uses general knowledge of English. Answers that are not definite and suggest a variety of options are not acceptable answers.
Input: Question: A few days ago, a friend and I were discussing how every "rule" of English spelling or pronunciation has an exception, and every exception has an exception as well. Then I brought up the rule of a ph cluster equaling an f sound (as in phonetic, elephant, morph, etc.) as a pronunciation rule that didn't have any exceptions I could think of. Is this a true hard-and-fast rule or does it have some exceptions as well? I'm not counting abbreviations such as pH scale. 
Answer: Ones that haven't been mentioned: upholstery upheld upheaval I took this further and ran the following fairly simple command in Linux that tries to solve this problem, I've commented each part of the command on the right in the interest of readability: look . | grep ph | # List words and filter out ones with ph. while read word ; do # Set variable $word to each word. espeak -qx "$word" | # Print phonetic pronounciation of the word. grep -q f || # If it doesn't have an f sound in it, echo "$word" # then print the word. done alphol Alphonist Alphonse Alphonsine Alphonsism Alphonso alphorn alphos alphosis archshepherd creephole cupholder haphazard haphazardly haphazardness lamphole loophole nonupholstered nympholepsia nympholepsy nympholept nympholeptic overshepherd peephole sheepherder sheepherding shepherd shepherdage shepherddom shepherdess shepherdhood Shepherdia shepherdish shepherdism shepherdize shepherdless shepherdlike shepherdling shepherdly shepherdry shepherdry Stephen sulpholeate sulpholeic taphole Theraphosa theraphose theraphosid Theraphosidae theraphosoid traphole undershepherd unshepherded unshepherding unupholstered uphand uphang upharbor upharrow uphasp upheal upheap uphearted upheaval upheavalist upheave upheaven upheld uphelm uphelya upher uphill uphillward uphoard uphoist uphold upholden upholder upholster upholstered upholsterer upholsteress upholsterous upholstery upholsterydom upholstress uphung uphurl Note that these results aren't perfect, its based on the phonetic information that the espeak program contains and also some slightly flawed logic that excludes words that have an 'f' in them. Like flophouse. I'd have to write a more sophisticated program to get better results. Another interesting thing you can do is calculate is the number of ph words overall vs. the list above. There are 12,148 words in the dictionary I'm using with 'ph' in them and there are 87 words above. So only about 0.72% of ph words are not pronounced with an 'f' sound.

no