A:国民党新军阀混战加剧
B:民众抗日救亡运动高涨
C:国民党政权内部急剧分化
D:国共两党由对峙走向合作
蜜蜂采蜜归来,发出声音的音调变低.原因是负重增加的情况下,蜜蜂翅膀扇动的频率( )
It soon became ____(显然) to everyone that he couldn't sing.