Which are the correct statements about the use case diagram below?

Question

I found this practice question online and I am very confused by it

Given the use case diagram below, select the CORRECT statement(s):

a. A user cannot Rebalance its portfolio before having all the stocks listed.

b. The customer service representative interacts with the system whenever a user rebalances the portfolio.

c. Every time a user interacts with Rebalance portfolio they must either buy or sell stocks.

d. Rebalance portfolio is only executed if buy new or sell stock decides.

e. The use cases are executed in the following order: 1) Rebalance portfolio 2) List stocks, 3) Buy new stocks, 4) Sell stocks.

I believe the options are A and C, since List Stocks must be included to rebalance the portfolio in the use case diagram. And C because both Sell stock and Buy new stock extends from Rebalance portfolio, so if user interacts with rebalance portfolio, they must either buy or sell stocks Am I correct?

Answer 1

Im am not posting a spoiler, only giving you a hint.

You find the answer in this old SO question What's is the difference between include and extend in use case diagram?.

In short, "extends" refers to optional parts of a use case, "includes" refers to mandatory parts which can be reused somewhere else or on its own. Now rethink your answer.