The correct answer is C. Extinguish the flame when the burner is not in use.
Step-by-step explanation
The Bunsen burner was invented by Robert Bunsen in 1857 and provides a very fast transmission of intense heat in the laboratory. The Bunsen burner consists of a vertical tube that is screwed to a metal foot with income for the flow of fuel, which is regulated through a key on the work table. In the lower part of the vertical tube, there are holes and a mobile metal ring or collar also drilled. By adjusting the relative position of these holes (tube body and collar respectively), which can be spherical or rectangular, it is possible to regulate the flow of air provided by the oxygen necessary to carry out combustion with the flame formation in the mouth or upper part of the vertical tube. Due to this, the Bunsen Burner is a useful tool in the laboratory but should be manipulated following safety measurements that include to avoid direct skin contact with fire, keep the instrument out of reach of children or using it without instructions from your teacher, and keep the fire off if it is not being used as this avoids possible burnings or accidentally begining a fire. So, the correct answer is C. Extinguish the flame when the burner is not in use.