D. marble i know this because i just had a test on this!
The whole human body is a lever system, that's how muscle work. Your joins are the fulcrum, your muscle contracts and hence is the effort. On the other side, whatever you're holding and the weight of your hand is the load. There are all 3 classes of lever system in your body.
As you can see in the picture presented below, the three classes of water have distinctive traits.
Pure substances contain only one element, they are not mixtures of different things.
The homogeneous mixtures have multiple elements, but they are so well blended together that you can't easily observe or separate them.
In heterogeneous mixtures, we can easily differentiate between different elements of the mixture.