You work as the application developer at Certkiller .com. Certkiller .com uses Visual Studio.NET 2005 as its application development platform. You are in the process of storing numerical values up to 2，100，000，000 into a variable and may require storing negative values using a .NET Framework 2.0 application. You are required to optimize memory usage. What should you do？ （）

A. Int32
B. UInt16
C. UInt32
D. Int16