In which of the following are hydrogels used? 1. Controlled drug delivery in patients 2. Mobile air-conditioning systems 3. Preparation of industrial lubricants. Select the correct answer using the code given below:

Hydrogels are used in all three applications. They are extensively used in controlled drug delivery systems, where they can release medicines at controlled rates in response to stimuli like pH or temperature. Hydrogels can be used in mobile/portable air-conditioning systems as desiccants or moisture absorbers, and in evaporative cooling applications. They are also used in formulating industrial lubricants and as friction-reducing agents. Their water-retaining property and tunable mechanical characteristics make them versatile across many sectors.