They would provide the final pieces of an unsolved puzzle.

How sexual reproduction evolved and survived is an unsolved puzzle.

Rather, these outbreaks are one small piece in the larger unsolved puzzle.

They were a strange phenomenon, one of the unsolved puzzles of geology.

The conference, after all, is devoted to new scholarly research: tricky empirical questions and unsolved theoretical puzzles.

The mere existence of unsolved puzzles within a paradigm does not constitute a crisis.

Players can visit certain areas in order to play undiscovered or unsolved puzzles that are left behind as the story progresses.

You know what a lot of unsolved puzzles it holds, and .

"Because I hate unsolved puzzles," he said, getting to his feet.

For the Demu are an unsolved puzzle, and always I would learn.