某铁路挡土墙墙背倾斜角α=9°，墙后填土，=40°，墙前与填土间摩擦角δ=20°，当墙后填土表面为水平连续均布荷载时，按库仑理论计算破裂角θ为（）。

A:20° B:26° C:31° D:38°

某土质边坡，γsat=20kN/m3，假设滑动面为平面，c=0，ψ=30°、一级边坡，Ks=1.35，求坡角α为（）。

A:20° B:24° C:23° D:25°

如图，O中，弦AD∥BC，DA=DC，∠AOC=160°，则∠BCO等于（）。

A:20° B:30° C:40° D:50°

如右图所示，在△ABC中，已知AB＝AC，AM＝AN，∠BAN＝30°。问∠MNC的度数是多少（）

A:15° B:20° C:25° D:30°

Passage Five
Temperatures on December 12
City High Low
Cleveland .................. 37° 31°
Columbia, S. C ............ 60° 27°
Columbus, Ohio ............ 41° 34°
Dallas .................... 81° 50°
Dayton. ................... 41° 33°
Decatur ................... 39° 30°
Denver .................... 49° 33°
Des Moines ................ 34° 27°
Detroit ................... 37° 28°
Dubuque ................... 30° 23°
Duluth .................... 19° 10°
Eau Claire ................ 24° 19°
El Paso ................... 79° 36°
Evansville ................ 52° 36°
Fairbanks ................. -31° -40°
Fargo ..................... 17° -2°
Flint ..................... 31° 26°
Flagstaff ................. 56° 31°
Great Falls ............... 14° 3°
Grand Rapids .............. 33° 26°
Green Ray ................. 24° 20°

What was the high temperature in Columbus, Ohio on December 12（）

A:81°. B:50°. C:41°. D:60°.

Passage Five
Temperatures on December 12
City High Low
Cleveland .................. 37° 31°
Columbia, S. C ............ 60° 27°
Columbus, Ohio ............ 41° 34°
Dallas .................... 81° 50°
Dayton. ................... 41° 33°
Decatur ................... 39° 30°
Denver .................... 49° 33°
Des Moines ................ 34° 27°
Detroit ................... 37° 28°
Dubuque ................... 30° 23°
Duluth .................... 19° 10°
Eau Claire ................ 24° 19°
El Paso ................... 79° 36°
Evansville ................ 52° 36°
Fairbanks ................. -31° -40°
Fargo ..................... 17° -2°
Flint ..................... 31° 26°
Flagstaff ................. 56° 31°
Great Falls ............... 14° 3°
Grand Rapids .............. 33° 26°
Green Ray ................. 24° 20°

What was low temperature in Flagstaff on this day（）

A:26°. B:-2°. C:3°. D:31°.

Passage Five Temperatures on December 12 City High Low Cleveland .................. 37° 31° Columbia, S. C ............ 60° 27° Columbus, Ohio ............ 41° 34° Dallas .................... 81° 50° Dayton. ................... 41° 33° Decatur ................... 39° 30° Denver .................... 49° 33° Des Moines ................ 34° 27° Detroit ................... 37° 28° Dubuque ................... 30° 23° Duluth .................... 19° 10° Eau Claire ................ 24° 19° El Paso ................... 79° 36° Evansville ................ 52° 36° Fairbanks ................. -31° -40° Fargo ..................... 17° -2° Flint ..................... 31° 26° Flagstaff ................. 56° 31° Great Falls ............... 14° 3° Grand Rapids .............. 33° 26° Green Ray ................. 24° 20°

What was low temperature in Flagstaff on this day（）

A:26°. B:-2°. C:3°. D:31°.

Passage Five Temperatures on December 12 City High Low Cleveland .................. 37° 31° Columbia, S. C ............ 60° 27° Columbus, Ohio ............ 41° 34° Dallas .................... 81° 50° Dayton. ................... 41° 33° Decatur ................... 39° 30° Denver .................... 49° 33° Des Moines ................ 34° 27° Detroit ................... 37° 28° Dubuque ................... 30° 23° Duluth .................... 19° 10° Eau Claire ................ 24° 19° El Paso ................... 79° 36° Evansville ................ 52° 36° Fairbanks ................. -31° -40° Fargo ..................... 17° -2° Flint ..................... 31° 26° Flagstaff ................. 56° 31° Great Falls ............... 14° 3° Grand Rapids .............. 33° 26° Green Ray ................. 24° 20°

What was the high temperature in Columbus, Ohio on December 12（）

A:81°. B:50°. C:41°. D:60°.