What should you do?

A SharePoint 2010 environment contains a Microsoft SQL Server 2008 R2 database instance named SP-SQL that hosts the databases for the farm.
You are upgrading the farm to SharePoint 2013.
You need to ensure that users can access the unmodified farm contents during the upgrade process.
What should you do?
A. Run the following Transact-SQL (T-SQL) statement for each content database and service application you plan to upgrade. ALTER DATABASE <database name>SET READ_ONLY;
B. Run the following command-line tool for each site collection in the content databases you plan to upgrade. Stsadm -o setsitelock -urKsite collection name> -lock readonly
C. Run the following Windows PowerShell cmdlets for each web application in the SharePoint 2010 farm you plan to upgrade. $db = Get-SPContentDatabaseSet- SPContentDatabase$db -Status Offline
D. Run the following Transact-SQL (T-SQL) statement for each content database and service application you plan to upgrade. EXEC sp_dboption, “read only”, “True”;