制作spacer层时，利用RIE刻蚀的什么性质可以保证将栅的表面和源漏表面的氮化硅刻掉 <br/>______

Which of the following is not a feature of CRISPR? A: Contain palindromic DNA repeats B: Have highly conserved spacer regions C: Provide adaptive immunity to Bacteria and Archaea D: Used as a molecular biology tool for genome editing