A Pulley
What the most useful machine is, is a matter of opinion. Some would argue that the wheel is the most useful machine, and others would argue that the lever is the most useful.
A simple random sample.
A lever! The most simple would probably be a form of lever, and this may also depend on the actual size of the "heavy rock".
Soil
Statistically speaking, the mean is the most stable from sample to sample. Whereas, the mode is the least stable statistically speaking from sample to sample.
The gas that contains the most molecules in a 5.0 L sample would be the one with the highest molar mass. This is because the number of molecules in a gas sample is directly proportional to its molar mass.
a stratified random sample
The sample with the lowest density would likely be the one that is the lightest for its volume. This can be achieved with materials like Styrofoam or a gas.
Which piece of laboratory apart it would most likely be used to evaporated E1 millimeters sample of a solution to drynes
A diamond sample would experience the most abrasion due to its hardness, which is the highest on the Mohs scale. Diamond is often used in cutting and grinding tools for its excellent abrasive properties.
The best ground work jobs that a Caterpillar backhoe are suited for at jobs that require large areas to be dug out, however, they are a multipurpose machine and can be used for other things as well.
To accurately identify what material sample A is most likely made of, I would need specific information about its properties, such as color, texture, weight, or any other distinguishing features. Common materials could include metals, plastics, wood, or fabrics, among others. If you can provide more details about sample A, I would be happy to help narrow it down further.