Why Is Gaining Research Experience Before Applying to Graduate School

Why is gaining research experience before applying to graduate school so important?

A) because it gives a faculty member who will write a letter of recommendation first-hand knowledge of your ability to handle graduate school demands
B) because it builds the kind of skills (e.g., teamwork, library navigation) that graduate school will require
C) because if you really don't like research, you can save yourself a lot of time and money by figuring out a different path
D) All of the answers are correct.