某型号汽车发动机的额定功率为6×l04W,在水平路面上匀速行驶时受到的阻力是1800N.在额定功率下,当汽车匀速行驶时,求:
—Why! I couldn't get you on the phone this morning.
—We ________ tennis in the yard when you phoned me.
A热带____ ①四季变化显著____ a有太阳直射现象
B南、北温带____ ②终年炎热____ b有极昼、极夜现象
C南、北寒带____ ③终年寒冷____ c无极昼、极夜也无太阳直射现象
如图是男女一些生殖器官的发育趋势图,请据图回答问题.