He tries ______ music well, so he practices ______ songs every day.
A:to learn; to sing
B:learning; singing
C:to learn; singing
D:learning; to sing
如图是模拟调光灯的电路图.电源电压恒为6V,小灯泡L的额定功率是6W,滑动变阻器R的最大电阻是20Ω.灯丝的电阻随温度的变化而变化.闭合开关S,当滑动变阻器的滑片P位于a端时,小灯泡正常发光.试求:
如图,函数y=2x和y=ax+5的图象交于点A(m,3),则不等式2x<ax+5的解集是( )
下列不属于青春期正常心理变化的是( )
—Believe it or not, I saw a UFO just now!