Which among the following is an example of insoluble impurities?

In water, two kinds of impurities can be present. These impurities make the water unfit to use. They are soluble impurities and insoluble impurities. Sand is an insoluble impurity.  Because when it is added to water, it does not dissolve but gets settled down in the water. Whereas salt and sugar are called soluble impurities because they get dissolved when they are added to the water.