i would say the best answer is d
The minerals are mostly characterized by the <u>Physical</u><u> </u><u>properties</u><u> </u><u>(</u><u>D</u><u>)</u> which includes the hardness, lustre, density etc. The mineralogists check the detailed view of minerals by using high powered microscope.
The minerals are chemical compounds which are formed as a result of physical processes or geological processes. They mostly occur in crystalline form. <u>For Example:</u> Cacite, Sulfur, Quartz etc
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The correct option is D. Organisms work best at their optimum temperature and pH, above and below these temperature they will not be able to function as expected. It is possible that the students above use different temperature and pH when they were carrying out their experiments, this will result in different efficiency rate by the yeasts.