Final answer:
In Sonnet 18, the word 'temperate' suggests that the person being addressed is calm and pleasant, and not prone to extremes, which corresponds to the definition 'c: agreeable.'
Step-by-step explanation:
In Sonnet 18, Shakespeare used the word "temperate" to describe someone as being more lovely and even-tempered than a summer's day. The definition that best fits this context is 'c: agreeable.'
Shakespeare's comparison suggests that the person he is speaking to is not subject to the extremes of a summer day which can have rough winds and varying temperatures, implying that the person is calm, pleasant, and not prone to sudden changes or extremes.
This phrase means that the person is even more beautiful and pleasant than a summer's day. The word 'temperate' in this context means moderate or mild, indicating that the person's qualities surpass those of a summer's day.