Application developers in your company create an assembly that contains a CLR function. This CLR function reads data from a spreadsheet, performs some calculations, and returns the data to a SQL Server 2005 computer. You need to register the assembly with SQL Server 2005 by using the CREATE ASSEMBLY statement and the least privileged security permission set. 
Which permission set should you use? （）

A. Default 
B. SAFE 
C. EXTERNAL_ACCESS 
D. UNSAFE