Final answer:
In stanzas 6-8, the term 'mucker' refers to someone who mishandles expensive supplies.
Step-by-step explanation:
In the context of stanzas 6-8, the term 'mucker' refers to someone who mishandles expensive supplies. This can be inferred from the line in stanza 6: 'He did with [china] what muckers do' which suggests that the person did something careless or clumsy with the delicate china. Furthermore, the term 'muckers' is used in contrast to the 'artists' mentioned in stanza 8, implying that muckers are individuals who lack the skill and finesse required to handle expensive supplies properly. Therefore, option A, 'someone who mishandles expensive supplies', is the correct interpretation of the term 'mucker' in stanzas 6-8.