What is a collection of key-value pairs called?

What is an online alternative to customers sending checks via mail?

a. currency exchange b. Western Union c. payment processor d. Moneygram

A stack is initially empty, then the following commands are performed: push 5, push 7, pop, push 10, push 5, pop which of the following is the correct stack after those commands (assume the top of the stack is on the left)?

a. 5 10 7 5 b. 5 10 c. 7 5 d. 10 5