Answer:
The correct answer to the following question will be Option B (Mainframe).
Step-by-step explanation:
Mainframe computers are computers that are mainly used by large companies for commercial applications; massive data analysis, including survey, business and client reports, commercial resource preparing, and transaction processing.
And Mainframe machine is so easy for use when a large organization, like a bank, can handle millions of transactions where no user intervention is required.
There's no other way that can make the transaction in millions. So, Option B will be the right answer.