对流层因为空气有强烈的对流运动而得名，它的底界为地面，上界高度随纬度.季节.天气等因素而变化。同一地区对流层上界高度（）
B
暂无解析
Iwouldlove________tothepartylastnightbutIhadtoworkextrahourstofinishareport.
WehavereceivedyourletterofSeptember12,______wearegladtoknowthatyouareinterestedinourelectricheaters.
Inourdepartment,everystudent_________after-schoolactivities.
She________everythingelseandconcentratedonthetaskbeforeher.