Which transaction isolation level should you use in sp1?

You use SQL Azure to store data used by an e-commerce application.

You develop a stored procedure named sp1.

Sp1 is used to read and change the price of all the products sold on the e-commerce site.

You need to ensure that other transactions are blocked from updating product data while sp1 is executing.

Which transaction isolation level should you use in sp1?
A . read committed
B . repeatable read
C . snapshot
D . serializable

Answer: D