The answer to this is C. Sand. If you are confused how this answer is reached, you first have to look at the various choices that are available. What can be clear about this choices? All of them are solid objects but another thing to note is that almost all of them can be counted easily.
You can take a look at the pillows that you have at home and count how many that you have. There is one thing that you cannot count and that is sand. No matter how hard you try to count sand, they are too fine to be counted. Some would rather count and collect stones because this can be easier to accomplish.
An investment means that you have stockpiled a resource for future use with the hopes of gaining a return on that money. Putting money in a savings account in any year, you will have a small positive return, just like clockwork.
Savings accounts are incredibly liquid, which ensures a low-risk investment with a low expected rate of return. The savings account not only gives you an opportunity to save your money for future use while making it very easy to access your funds.
If you invest money in a savings account, you may get 3%-6% interest on the funds that you have maintained for a period of time.