Which code fragment, when inserted at line n1, prints 1…

Given the code fragment:
List<Integer> list1 = Arrays.asList(10, 20);
List<Integer> list2 = Arrays.asList(15, 30);
//line n1
Which code fragment, when inserted at line n1, prints 10 20 15 30?

A.
Stream.of(list1, list2)
.flatMap(list -> list.stream())
.forEach(s -> System.out.print(s + “ “));

B.
Stream.of(list1, list2)
.flatMap(list -> list.intStream())
.forEach(s -> System.out.print(s + “ “));

C.
list1.stream()
.flatMap(list2.stream().flatMap(e1 -> e1.stream())
.forEach(s -> System.out.println(s + “ “));

D.
Stream.of(list1, list2)
.flatMapToInt(list -> list.stream())
.forEach(s -> System.out.print(s + “ “));