Условие:
var task = F1();\nConsole.Write("A ");
\nawait Task.Delay(750);\nConsole.Write("B ");
\nawait task;
\nawait Task.Delay(750);\nConsole.Write("C ");
\nasync Task F1()
{
await Task.Delay(500);
Console.Write("D ");
await Task.Delay(500);
Console.Write("E ");
await Task.Delay(500);
Console.Write("F ");
}

