Answer:
Common stocks
Step-by-step explanation:
Out of all the given options the Common stocks are considered to be the most risky investment on comparison to others.
This is due to the fact that the returns from these investments are uncertain. because if there is a loss of a particular company whose stocks belongs ,the stockholders will not get any amount as return against their investment.
Also, If the condition of company's bankruptcy arises or it goes bankrupt, the common stockholders are below the other class of bond like the corporate bonds and mortgage bonds. Thus, the stockholders will not receive the money until the shareholders, bondholders, and other debt of the company have been fully paid from the assets that is leftover.
Hence, the correct answer is option (d)