Four children were born at City Hospital yesterday. Assume each child is equally likely to be a boy or a girl. Which of the following outcomes is most likely? 
选项为:A:all $4$ are boys  B:all $4$ are girls  C:$2$ are girls and $2$ are boys  D:$3$ are of one gender and $1$ is of the other gender  E:all of these outcomes are equally likely  请回答其中一个选项.