哪种写法会先启动两个独立调用，再等待任一结果？

哪种写法会先启动两个独立调用，再等待任一结果？

1. `val a = async { first() }.await(); val b = async { second() }.await()`
2. `val a = async { first() }; val b = async { second() }; use(a.await(), b.await())`
3. `val a = first(); val b = second(); use(a, b)`
4. `GlobalScope.async { first(); second() }.await()`