Which Transact- SQL statement should you use?

You are a database developer of a Microsoft SQL Server 2012 database. You are designing
a table that will store Customer data from different sources. The table will include a column
that contains the CustomerID from the source system and a column that contains the
SourceID. A sample of this data is as shown in the following table. You need to ensure that

the table has no duplicate CustomerID within a SourceID. You also need to ensure that the
data in the table is in the order of SourceID and then CustomerID.
Which Transact- SQL statement should you use?

A.
CREATE TABLE Customer
(SourceID int NOT NULL IDENTITY,
CustomerID int NOT NULL IDENTITY,
CustomerName varchar(255) NOT NULL);

B.
CREATE TABLE Customer
(SourceID int NOT NULL,
CustomerID int NOT NULL PRIMARY KEY CLUSTERED,
CustomerName varchar(255) NOT NULL);

C.
CREATE TABLE Customer
(SourceID int NOT NULL PRIMARY KEY CLUSTERED,
CustomerID int NOT NULL UNIQUE,
CustomerName varchar(255) NOT NULL);

D.
CREATE TABLE Customer
(SourceID int NOT NULL,
CustomerID int NOT NULL,
CustomerName varchar(255) NOT NULL,
CONSTRAINT PK_Customer PRIMARY KEY CLUSTERED
(SourceID, CustomerID));