The following precautions were listed for the experiment on determination of melting point of ice. The incorrect precaution is :
A. The bulb of the thermometer should be kept surrounded with crushed ice
B. Ice should be stirred regularly to keep a uniform temperature throughout
C. The final temperature should be noted by keeping the eyes in line with the level of mercury
D. Only the tip of the bulb of the thermometer should just touch the crushed ice