Question

Unexpectedly, they sang transitive or intransitive

Answer 1

Answer:It can be either

Explanation:

In the first, “sang” is a transitive verb with “Happy Birthday” as its object. But “sang” has no object in the second sentence (i.e., we don't specify what we were singing). As such, “sang” can be either transitive or intransitive depending on how we use it.