"unsolved puzzle" is a correct and usable sentence in written English.
You can use it to describe a problem that has not yet been solved. For example, "The mystery of the missing artifacts is still an unsolved puzzle."
We are never told how any of these sightings was explained; the flags become an unsolved puzzle.
Presumably, that is why dividend-free shares have become the club tie of America's high-growth companies.Dividends are still an unsolved puzzle for financial economists, eluding any single theory.
As for Mr. Clinton's marriage, which Mr. Klein suggests lies at the heart of many of the mysteries of his presidency, it remains an unsolved puzzle: "Over time," he writes, "I decided that the wisest course regarding the Clinton marriage was to be indiscriminately credulous, to believe all the stories".
Why is it then that the "question of animal culture" persists in being a controversial, unsolved puzzle?
Despite hundreds of studies on the Prisoner's Dilemma (PD) game, understanding about network reciprocity remains a unsolved puzzle.
"It's an intriguing suggestion to account for an unsolved puzzle," astronomer Ray Jayawardhana of the University of Toronto in Canada says.
Only when puzzles repeatedly prove recalcitrant does the community begin to develop a sense that something may be amiss; the unsolved puzzles acquire a new status, being seen as anomalies.
Instead, he declares that the crash "ranks high on the list of unsolved puzzles for scholars" who have been unable to determine "what role, if any, it played in bringing on the grinding depression that followed".
An unknown language in an unknown script is the linguistic equivalent of a locked-room mystery, and despite the efforts of investigators around the globe, Linear B endured for more than 50 years as one of the world's great unsolved puzzles.
The physiological roles of silent genes are still unsolved puzzles and their application potentials are unexplored.
Not taking the sex of the cell into account can lead to life-threatening consequences and leave researchers with unsolved puzzles.
