A stock is a term used to describe the certificates you have when you own a company. Stocks are one of the high favorites when it comes to investments, because though they are quite risky, they tend to become extremely valuable over time. It can be said that the reason for this is because the industries that have high value now have become bigger over time. Another reason is because the company is well-managed, and stability is a good lure for many investors, thus rising the value of the stocks. When there are many demands for the product, the company stocks also tend to be more valuable over time.
Thus the answer to the question above is (D) all of the above.