You’d better book the tickets in advance; _______ we may miss the concert.
In the dark street, there wasn’t a single person _____ she could turn for help.
She was more headstrong than ______.
The car ______ at the present speed until it reaches the foot of the mountain at about ten o’clock tonight.
Though ______, many laws of nature exist.
_____, I couldn’t find a solution to the problem.