. — Excuse me, did you notice whether the No. 18 bus had gone by?

— Not ______ I began to stand here.

A. as                            B. since                 C. when                D. while

 — Excuse me, did you notice whether the No. 18 bus had gone by?

— Not ______ I began to stand here.

A. as             B. since            C. when         D. while

―Excuse me, did you notice whether the No. 18 bus had gone by?

―Not ______ I began to stand here.

       A. as                     B. since                        C. when                       D. while

--- Excuse me. Did you notice whether the No 108 bus had gone by?

--- Not ______ I began to stand here.

A. until　　　　 B. once　　　　　 C. since　　　　 D. while

Death Valley is one of the most famous deserts in the United States, covering a wide area with its alkali sand Almost 20 percent of this area is well below sea level, and Badwater, a salt water pool, is about 280 feet below sea level and the lowest point in the United States.
Long ago the Panamint Indians called this place “Tomesha”— the land of fire. Death Valley’s present name dates back to 1849, when a group of miners coming across from Nevada became lost in its unpleasantness and hugeness and their adventure turned out to be a sad story. Today Death Valley has been declared（宣告）a National Monument（纪念碑）and is crossed by several well-marked roads where good services can be found easily. Luckily the change created by human settlement has hardly ruined the special beauty of this place.
Here nature created a lot of surprise, almost like the sights on the moon, ever-changing as the frequent（频繁的）wind moves the sand about, showing the most unusual colors. One of the most surprising and variable（多变的）parts of Death Valley is the Devil’ s Golf Course, where it seems hard for one to tell reality from terrible dreams. Sand sculptures（沙雕）stand on a frightening ground, as evening shadows move and lengthen.
【小题1】.. _______ is the lowest place in the desert.