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:

1. (a) 1 onlyCorrect answer
2. (b) 1 and 2 only
3. (c) 2 and 3 only
4. (d) 1, 2 and 3

Answer: (a)