Always ask, then you can tell to get it done.
You may ask, but they may not necessarily know the answer. If you use leading questions then this is an acceptable method.
If you "Ask", sometimes they will respond. But more often then not you will get a "blank look", unless you give them the option of some possible answers, where they just have to pick one rather then come up with their own thoughts on the subject.
I agree and asking open ended questions will also help in obtaining the answer to the questions you have presented.