Final answer:
The inference that Marlow has a condescending attitude toward the native population is best supported by the use of terms like 'pure' and 'rudimentary' to describe souls, implying a hierarchy that devalues the natives.
Step-by-step explanation:
The inference best supported by the excerpt that refers to Marlow is that he has a condescending attitude toward the native population. The extract explores the themes of colonialism and humanitarianism. The phrase "But you cannot compromise my humanity in order that you explore your own ambiguity" indicates a strong sentiment of being looked down upon, which implies that Marlow, or Europeans in general, are seen as having a superior attitude towards the colonized people.
Furthermore, the use of terms like 'pure' and 'rudimentary' to describe souls in the context of the excerpt suggests a hierarchy of valuation of human essence, with Europeans at the top and natives being devalued. This clearly establishes the condescending attitude Marlow has towards those who are not European.