Answer:
1. /p/ [voiceless stops]
2. /t/ [voiceless stops]
3. /k/ [voiceless stops]
/p/, /t/, /k/ are consonant sounds which have voiceless stops. These sounds are also aspirated at the beginning of words- i.e when pronounced, there is usually a forceful expulsion of air in words like "top", "tap", "kill", etc.
When the sounds are used at the end of words or joined with some consonants, they are not aspirated e.g drop, stop, etc.
4. /m/ [nasal stops]
When pronouncing nasal stops, the velum usually lowers to allow a free flow of air from the nose.
Examples of words that have nasal stops are:
"mouth", "mud", etc.
