Answer:
A. a mutual fund 
Step-by-step explanation:
A mutual fund - 
It is a type of financial vehicle , where the money collected by the investors , is pooled and then further invested in securities , like the bonds or stock market is referred to as mutual fund . 
Any investor can invest their money in the mutual funds , it is a indirect form of investing in the stock market . 
The returns obtained by mutual funds are dependent on the stock market .
Hence , from the given information of the question , 
The correct option is A. a mutual fund .