关于比热容,下列说法正确的是( )
如图,在Rt△ABC中,∠BAC=90°,∠ABC的平分线BD交AC于点D,DE是BC的垂直平分线,点E是垂足.已知DC=5,AD=2,则图中长为21的线段有( )
—How about joining us in the summer camp?—I wish I could, ___________ I have to practice for the piano test.
读汕头农业主要产业产值图(如图),回答下题。