Answer:
The sentence it will introduce will be contrasting to the sentence(s) before that.
Explanation:
E.g. I woke up late. <em>However</em>, I got to school on time.
["However" here contrasted the idea that "I" might be late for school since "I" woke up late]
Answer:
the celebratory dinner
Explanation:
the sentence is basically about the dinner, and roast beef & mashed potatoes is what the subject (the celebratory dinner) <em>is.</em>
Since 'next' is a time-order word, you need another.
'Then' is a time-order word. You are not stating a 'fact', nothing happened abruptly, or 'suddenly', and you aren't comparing anything, 'similarly'.
