她没来参加聚会，想必当时身体不舒服。
She mustn't have been feeling well, or she would have come.
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mustn't英 /ˈmʌsnt/|美 /ˈmʌsnt/
been英 /biːn/|美 /bɪn/
解释
mustn't have been + v-ing 对过去进行状态做否定推断：从缺席推断她当时身体不适。
She mustn't have been feeling well, or she would have come.
mustn't have been + v-ing 对过去进行状态做否定推断：从缺席推断她当时身体不适。