in the river for five hours, the thief looked very pale and exhausted.

________ him before, I didn't recognize him.

______ in the chimey for five hours, the thief looked very pale and tired.

Though ______, many laws of nature exist.

　 A. not having been discovered 　 B. having not been discovered

　 C. not having discovered 　    D. having not discovered

Though ______, many laws of nature exist.

　 A. not having been discovered 　 B. having not been discovered

　 C. not having discovered 　     D. having not discovered