Part 1. Definition
Given the Target and Argument texts detect the stance that the argument has towards the topic. There are three types of stances "in favor", "against", and "neutral". 
Part 2. Example
Topic: Three Gorges Dam
 Argument: The Three Gorges Dam is a cause of corruption.
Answer: against
Explanation: Here, argument is against the given topic, three gorges dam. Hence, the answer is "against".
Part 3. Exercise
Topic: Ecotourism
 Argument: Ecotourism economically benefits local people.
Answer:
in favor