Tom is one of _________ students in my class .Yes . He usually prefers _________ at home to playing outside .
A:the most hard-working , studying
B:more hard-working , to study
C:the most hard-working , to study
D:more hard-working , studying
除去下列物质中混入的少量杂质(括号中的物质为杂质)所设计的实验方案或操作中,合理的是( )
某中学八年级一班的同学对一块农田观察后,画了一副农田生态系统的食物网图,请你分析,下列哪项是正确的( )