Supplies originally cost $$600,$ but only $$150$ worth of supplies were used this period. The adjusting entry would be

a$.$ debit Supplies Expense, $$150$; credit Supplies, $$150.$

b$.$ debit Supplies, $$450$; credit Supplies Expense, $$450.$

c$.$ debit Supplies Expense, $$450$; credit Supplies, $$450.$

d$.$ debit Supplies, $$150$; credit Supplies Expense, $$150.$