如果∠1+∠2=90°，∠3+∠4=90°，且∠1=∠3，根据______，于是有∠2=∠4．

---_______ matters to do the job well

---what you are or where you come from? [ ]

A. Which is it that

B. What it is that

C. Which it is that

D. What is it that