Which of the following best describes someone who is 'soporific'?

The term 'soporific' is used to describe something that causes or induces sleep, making the correct answer one that aligns with this definition. In this context, a person or thing that is soporific would have a calming effect, potentially making it difficult for someone to remain awake or alert. For instance, a dull lecture or a tranquil environment can both be considered soporific, as they can lead to drowsiness.

In contrast, options that suggest energy, stimulation, or challenge do not align with the meaning of soporific. 'Energetic and lively' conveys a sense of excitement and activity, while 'stimulating and exciting' implies engagement and alertness. Finally, 'challenging and thought-provoking' denotes a stimulating intellectual experience rather than one that induces sleep. Thus, 'calming and sleep-inducing' is the most accurate description of someone or something that can be characterized as soporific.