After the following program is finished, how many bytes are written to the file t.dat?

```
import java.io.*;

public class Test {
public static void main(String[] args) throws IOException {
DataOutputStream output = new DataOutputStream(
new FileOutputStream("t.dat"));
output.writeShort(1234);
output.writeShort(5678);
output.close();
}
}
```
a. 2 bytes.
b. 4 bytes.
c. 8 bytes.
d. 16 bytes.

b. 4 bytes.