Hola!! Your answer for this question is oficina de correos.
1.) If you translate the question you get:
I need to buy an envelope in a ____
post Office
Bank
Bakery
Museum
2.) From the options, the best answer will be the Post Office. You can buy an envelope there.
The answer is: <span>The </span>unit of measure concept<span> is a standard convention used in accounting, under which all transactions must be consistently recorded using the same currency.</span>