The answer is the amputation of the lieutenant's arm. None of the other options are events in the story. The lieutenant returns home and we don't know the outcome of the battle. There is also no evidence he was ever ill.
/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.