The stars can only be seen at night.

absolute or qualified?

The correct answer is:

Absolute

Explanation:

It is possible to establish this statement as absolute, since absolute statements are sentences that express or reaffirm a specific kind of information without letting space to have any modifier for the given information. e.g. "The stars can only be seen at night."

On the other hand, it is probable to find qualified statements that normally include words that qualify or suggest something about the given information in the statement.  e.g. "Sometimes, it is possible to see the stars at night"

remember, the goal of an adjective clause is to add more information to a noun or a pronoun. as you can see from the examples above, you can add information by including a longer adjective clause or tighten up a sentence by turning the adjective clause into an adjective phrase.