Five sentences related to a topic are given below. Four of them can be put together to form a meaningful and coherent short paragraph. Identify the odd one out. Choose its number as your answer and key it in.

1. Our smartphones can now track our diets, our biological cycles, even our digestive systems and sleep-patterns.

2. Researchers have even coined a new term, “orthosomnia”, to describe the insomnia brought on by paying too much attention to smartphones and sleep-tracking apps.

3. Sleep, nature’s soft nurse, is a blissful, untroubled state all too easily disturbed by earthly worries or a guilty conscience.

4. The existence of a market for such apps is unsurprising: shift work, a long-hours culture and blue light from screens have conspired to rob many of us of sufficient rest.

5. A new threat to a good night’s rest has emerged – smart-phones, with sleep-tracking apps.