单选题：Given:

Given:
```Java
class Century implements Runnable {
public void run() {
for ( int year = 1900; year < 2000; year++ ) {
System.out.println(year);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
}
}
System.out.println("Happy new millennium!");
}
}
public class CountUp {
public static void main(String[] args) {
Century ourCentury = new Century();
// put your line here
}
}
```
There’s a missing line in CountUp.main(), which is to begin the thread defined in Century. Which is the proper code: @[D](2)

A. Thread t = new Thread(this); t.start();
B. Thread t = new Thread(ourCentury); ourCentury.start();
C. Thread t = new Thread(this); t.start(ourCentur);
D. Thread t = new Thread(ourCentury); t.start();



A.Thread t = new Thread(this); t.start();
B.Thread t = new Thread(ourCentury); ourCentury.start();
C.Thread t = new Thread(this); t.start(ourCentur);
D.Thread t = new Thread(ourCentury); t.start();


答案：D