You must have dial an incorrect number.
妳壹定沒撥對電話。
He must've missed the 6: 30 train.
他壹定沒趕上6點半的那班火車。
Depend upon it, we shall succeed.
沒問題，我們壹定能成功。
This pen must have run out of ink.
這鋼筆壹定是沒墨水了。
She must have missed the notice in the paper yesterday.
她壹定是沒看到昨天報上的通告。