Which of the following is an example of endothermic process ?

According to the NCERT text:

• Formation of slaked lime (Activity 1.4) is highly exothermic as calcium oxide reacts vigorously with water, releasing a large amount of heat:

$$\text{CaO(s)} + \text{H}_2\text{O(l)} \rightarrow \text{Ca(OH)}_2\text{(aq)} + \text{Heat}$$

• Decomposition of vegetable matter into compost is explicitly stated in the text as an example of an exothermic reaction.
• Digestion of food involves the breakdown of carbohydrates into glucose, which then combines with oxygen in our cells to release energy (respiration), making it an exothermic process:

$$\text{C}_6\text{H}_{12}\text{O}_6\text{(aq)} + 6\text{O}_2\text{(aq)} \rightarrow 6\text{CO}_2\text{(aq)} + 6\text{H}_2\text{O(l)} + \text{energy}$$

• Dissolution of ammonium chloride in water absorbs heat from the surroundings, resulting in a fall in temperature, which makes it an endothermic process.