In which of the following are hydrogels used?1.Controlled drug delivery in patients2.Mobile air- conditioning systems3.Preparation of industrial lubricantsSelect the correct answer using the code given below:

1. A

   1 only

   1 only. Hydrogels are used in controlled drug delivery. Mobile AC and industrial lubricants are not the keyed uses here.

2. B

   1 and 2 only

   1 and 2 only. Statement 2 is not keyed.

3. C

   2 and 3 only

   2 and 3 only. Drops the true biomedical use.

4. D

   1, 2 and 3

   All three. The paper keys only drug delivery.

Summary. Official key is (a) 1 only. Hydrogels (water-swollen polymer networks) are used to release drugs in a controlled way. On this paper, mobile air-conditioning and industrial lubricants are not counted as hydrogel uses. So only 1.