Answer:
Buying on the margin.
Step-by-step explanation:
Buying on the margin is term which is stated as the amount of money borrowed from the broker in order to purchase or buy the stock. It can be considered as a loan from the brokerage. It allows or helps the person to buy more stock than the person able to. In order to trade on margin, one needs to have a margin account.
In this scenario, Alex wanted to invest in the stock market, but did not have money to buy all the shares. So, Alex borrowed the money which is called as buying on margin.