D("foo.com", "none",
    A("@", "1.2.3.4", TTL("300s")),
    A("a", "1.2.3.5", TTL("300")),
    A("b", "1.2.3.6", TTL("3m")),
    A("c", "1.2.3.7", TTL("3h")),
    A("d", "1.2.3.8", TTL("3d")),
);