A Researcher Finds That,on Average,the Firstborns at One High School

Multiple Choice

A researcher finds that,on average,the firstborns at one high school have higher grades than second- and third-born children.Other than birth order,what else might explain this result?

A) Children who get good grades in elementary school tend to do well in high school also.
B) ​Some parents give their children more attention than others do.
C) ​More recent generations tend to do better on tests than those born earlier.