suddenly可以单独放在开头吗

可以单独放开头，例如：

1、Suddenly the horse lurched to one side and the child fell off.马突然歪向一边，小孩就摔了下来。

2、Suddenly the boat tilted to one side.小船突然倾向一侧。

3、Suddenly it clicked ─ we'd been talking about different people.我们突然领悟到原来我们谈论的不是同一个人。