Final answer:
Based on common storytelling structure and without the specific text, the earliest event in Harriet's life would likely be Mr. Winter finding Harriet at the pool and asking her to babysit, as it serves as an initiating event.
Step-by-step explanation:
The question asks which event occurs first chronologically in Harriet's life based on the provided excerpts. Without having the specific text where these events happen, one would have to speculate based on general storytelling and plot development. Typically, an event like 'Mr. Winter finds Harriet at the pool and asks her to babysit' (a) would be an initiating event. This could logically happen before 'Harriet holds baby Andrea' (b), as she would likely meet the baby after agreeing to the responsibility of babysitting. Similarly, 'Mr. Winter attempts to explain the motives of his wife' (c) typically would follow the establishment of a relationship initiated by the babysitting offer. Lastly, 'Harriet is unable to open the door to the nursery' (d) is an event that suggests she is already involved in the situation and thus would occur after the initial offer to babysit.
Without the context from the specific book that discusses Harriet's life, these guesses are speculative. If we are assuming the events relate to a common narrative structure, we would likely see the order of events starting with the offer to babysit as the initiating incident.