Several medicines that treat human diseases have been sourced from plants in tropical rainforests. for example, quinine, which is used to treat malaria, was originally isolated from cinchona plants in south american rainforests. as only approximately 10% of the plants in rainforests have been investigated for medicinal compounds, researchers predict that there may be many more plants with medicinal properties yet to be discovered in rainforests. deforestation of rainforests would most likely affect such plants by a)habitat loss b)pollution c)exploitation which could result in a) use b)growth c)extinction of some some plants with medicinal properties. this situation represents a risk to a)indirect benefits b)direct costs c)indirect costs d)direct benefits humans receive from ecosystems.