11.   Its place of origin is a mystery, but some scientists wonder how it acquired all the hardy properties required of a space traveler.

12.   Its place of origin is a mystery but some scientists wonder how it acquired all the hardy properties required of a space traveler.

13.   Like the rest of us, scientists have long wondered why, exactly, children must become teen-agers.

14.   Looking ahead, scientists were wondering what the weather would be like on Mars when the spacecraft arrives.

15.   Scientists have long wondered whether human behavior, too, is influenced by pheromones, because people possess a vomeronasal organ.

16.   Scientists have long wondered why some people become depressed in the winter, suffering from a condition called seasonal affective disorder or SAD.

17.   Scientists have long wondered why there is so much sex in the world.

18.   Scientists have often wondered why so many houses in California remain standing after an earthquake.

19.   Scientists have wondered ever since what they were.

20.   Scientists have long wondered how women like Otieno are able to carry so much so easily.