What do we know about Beethoven's father from the text?

　　定位到文中第一段的第一、二句，"At an early age, Beethoven took an interest in music. His father taught him day and night. Without doubt, the child was gifted."，贝多芬很小就对音乐感兴趣。他父亲日夜教他。毫无疑问，这孩子很有天赋。由此可以推断出，贝多芬的第一任老师是他的父亲。故选D。