A Student Titrated Extracted Chloride from a Soil Sample with 0.1

A student titrated extracted chloride from a soil sample with 0.1 M silver nitrate.During the titration he performed the following actions while operating the buret. -Washed the buret with silver nitrate solution
-Drained titrant slowly
-Delivered a fraction of a drop near end point
-Read bottom of concave meniscus
-Avoided parallax
-Accounted for graduation thickness in readings
His instructor notes on the student's lab report that the student forgot to____________________ when operating his buret.

A) eliminate air bubbles
B) estimate reading the buret to 1/10 of a division
C) fill the buret to exactly 0.00 mL
D) eliminate air bubbles and fill the buret to exactly 0.00 mL.
E) eliminate air bubbles and estimate reading the buret to 1/10 of a division.