The correct option is A Upset
The passage speaks about how a single cup of tea requires the work of thousands of people, but we've never stopped to think about it. We have our own schedule formed, from the time we wake up. Every morning there's a particular time that the milk van supplies the milk, so that's also a part of our schedule, on the basis of which we make our tea and breakfast. When the van gets late in the morning, it disturbs this schedule of ours, hence we get 'agitated'. 'Agitated' means 'to get disturbed'. From the options given below, the one closest to the meaning of 'agitated' is 'upset' as it also means 'to be disturbed' as it's out of the daily time that one expects someone/thing to arrive, so something arriving late can upset/disturb one's timing. Hence option A is correct. 'Angry' is a very strong emotion, a feeling of resentment which is caused by something severe, whereas the milk van coming late is not a situation so severe to make someone angry. Hence 'agitated' does not mean 'angry' and option B is incorrect. 'Serious' means 'something that is critical and requires deep thought'. This does not mean the same as agitated, we would not go into a deep thought if the van came late, hence option C is incorrect. 'Unhappy' is a state of an emotion, 'sadness', it can last for a while, but it doesn't have the same meaning as agitated, as we would not be sad if the milk van arrived late, hence option D is incorrect.