A:Because he has to do his homework.
B:Because he hates to do the dishes.
C:Because he has to make his bed first.
下列句子中,标点符号的使用正确的一句是( )
以下不属于排泄废物的是( )
( ) Why do you like this study?
某校学生在开展研究性学习时,进行人类遗传病方面的调查研究.如图是该校学生根据调查结果绘制的某种遗传病的家系图(显、隐性基因用A、a表示).请分析回答: