Final answer:
The most supportive text feature for the excerpt about Mary Kingsley from 'Into the Unknown' is a map of her travels up the Ogoou River in 1895, providing context and a visual representation of her journey.
Step-by-step explanation:
When reading the excerpt about Mary Kingsley from Into the Unknown by Stewart Ross, and considering which text feature best supports the excerpt, it seems that a map of Kingsley's travels up the Ogoou River in 1895 would be the most relevant and helpful. This visual aid would provide students with a geographical context of Kingsley's journey, complementing the detailed narrative and offering a visual representation of her exploration mentioned in the text. It would help students better understand the scale and scope of her travels, as well as the geographical challenges she might have encountered.