关于美国农业生产有利条件的叙述,正确的有①本土大部分属温带和热带,水热条件好 ②中部平原地区,地势平坦广阔,土壤肥沃 ③交通运输便利 ④工业发达,科技力量雄厚
A:①②③
B:①②④
C:①③④
D:②③④
下列比较研究中,能直观说明生物由简单到复杂进化趋势的是( )
已知四边形ABCD,∠ABC=45°,∠C=∠D=90°,含30°角(∠P=30°)的直角三角板PMN(如图)在图中平移,直角边MN⊥BC,顶点M、N分别在边AD、BC上,延长NM到点Q,使QM=PB.若BC=10,CD=3,则当点M从点A平移到点D的过程中,点Q的运动路径长为____.
Sunday,June 1
Dear Tony,
Now we are having fun at Tian'anmen Square. The weather is fine. There are many people here. We'll visit the Bird's Nest and the Water Cube. In the evening,we'll have Beijing Duck. I love Beijing. I hope you will come to China soon.
Your friend,
Ben
Tony White__
78 Flower Road__
New York,CBE779D,USA