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
《三国演义》主题曲中“滚滚长江东逝水,浪花淘尽…”这句话说明对河流流向起决定作用的是
写出“对顶角相等”的逆命题 ____
结合材料,回答下列问题: