public render(){
    ...
        <MyChildComponent
            optionsA={this.props.OptionsA} //give some properties to your Component
            optionsSelected={this.optionsSelected.bind(this)} //give a CallBack
         />
    ...
}

...

private optionsSelected(selection){
// DO SOMETHING
}
    ...

public render() {
...
    <myChildDropDown
       onChanged={(event) => this.props.optionsSelected(event)}
     />
...
}