6. You are going to use a dropper bottle to slowly add ethanol to the test tube. Position the dropper so that the drops run down the side of the test tube. Slowly
add drops until the test tube is half full. The ethanol should form a separate layer
above the filtered solution. Record what you observe.

7. Place the tip of the stirring rod at the point where the two layers meet as shown in
Figure 2. As you gently twirl the rod, bend down so you can observe what is
happening at eye level. Record what you observe.

8. After you dispose of the materials as instructed by your teacher, wash your hands
thoroughly with soap and warm water.

the real answer is b. scintillation counter

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!