Question

explain the difference in pronunciation with reference to the sounds [ p, t, k ] in the following examples, show how the difference accrues examples stop and spot, tin and stone, skirt and kick

Answer 1

In International Phonetic Alphabet, [p, t, k] retain their own pronunciation. They are "Voiceless" when you make its sound but has puff of air called aspiration. 

The pronunciation of P is like that of B but it is voiceless. Make a sudden exhale and pronounce the 'p' sound with an explosive breath.
Try to pronounce 'stop' and 'spot'
- spot contains an aspirated version of /p/, with a puff of air after the stop is released; [p^h]
- stop contains a plain /p/, without a puff of air after the stop; this is written just [p] 

The pronunciation of T is voiceless. Make a sudden exhale and pronounce the 't' sound with an explosive breath.
Try tin and stone
- stone contains an aspirated version of /t/, with a puff of air after the stop is released; [t^h]
- tin contains a plain /t/, without a puff of air after the stop; this is written just [t] 

The pronunciation of S is voiceless. Make a sudden exhale and pronounce the 's' sound with an explosive breath.
Try skirt  and kick
- skirt contains an aspirated version of /k/, with a puff of air after the stop is released; [k^h]
- kick contains a plain /k/, without a puff of air after the stop; this is written just [k]