All actions to address climate change ultimately involve costs. Funding is vital in order for countries like India to design and implement adaptation and mitigation plans and projects. The problem is more severe for developing countries like India, which would be one of the hardest hit by climate change, given its need to finance development. Most countries do indeed treat climate change as real threat and are striving to address it in a more comprehensive and integrated manner with the limited resources at their disposal.

With reference to the above passage, the following assumptions have been made:
1. Climate change is not a challenge for developed countries.
2. Climate change is a complex policy issue and also a development issue for many countries.
3. Ways and means of finance must be found to enable developing countries to enhance their adaptive capacity.

Which of the above assumptions is/are valid?

The correct option is 2 and 3 only.

Let us analyze the validity of each assumption step-by-step based on the provided passage:
1. Assumption 1: "Climate change is not a challenge for developed countries."
The passage states that all actions to address climate change involve costs, and most countries treat climate change as a real threat. It highlights that the problem is more severe for developing countries due to their development financing needs, but this does not imply that developed countries face no challenge at all. Therefore, Assumption 1 is invalid.
2. Assumption 2: "Climate change is a complex policy issue and also a development issue for many countries."
The passage mentions that countries are striving to address climate change in a "comprehensive and integrated manner" (making it a complex policy issue) and notes the specific challenge for developing countries like India "given its need to finance development" (making it a development issue). Thus, Assumption 2 is valid.
3. Assumption 3: "Ways and means of finance must be found to enable developing countries to enhance their adaptive capacity."
The passage explicitly states that "Funding is vital in order for countries like India to design and implement adaptation and mitigation plans and projects," and refers to the constraints of "limited resources at their disposal." This directly supports the assumption that financing pathways must be found to bolster adaptive capacity. Thus, Assumption 3 is valid.

Consequently, only assumptions 2 and 3 are valid, making "2 and 3 only" the correct answer choice.