1. I don't know who to say.

2. I don't know who to say about.
3. I don't know who I should say to.
4. I don't know who should say.
5. I don't know whom to say.
6. i don't know whom to say about.
(Which expressions are right?)

when was robin hood born

#4 is correct. In that one "who" is the subject. You need "whom" when that is an object.

#5 could be: "I don't know whom to tell." Here you would tell something (direct object) to someone (indirect object)

Sra

First, Lidya, if you have a question, it is much better to put it in as a separate post in <Post a New Question> rather than attaching it to a previous question, where it is more likely to be overlooked.

As far as I know, Robin hood is a folklore hero rather than a real person. However, since this is not my area of expertise, I searched Google under the key words "Robin Hood birth" to get these possible sources:

http://www.britainunlimited.com/Biogs/Hood.htm
http://wiki.answers.com/Q/What_is_the_date_of_Robin_hood's_birth

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.

I hope this helps. Thanks for asking.

Out of the six expressions you provided, four of them are grammatically correct:

1. "I don't know who to say." - This sentence is incomplete and lacks clarity. It needs further information to make sense.

2. "I don't know who to say about." - This sentence is grammatically correct. It indicates that you are unsure about whom to mention or talk about.

3. "I don't know who I should say to." - This sentence is grammatically correct. It implies that you are uncertain about the person or people to whom you should communicate a message.

4. "I don't know who should say." - This sentence is incomplete and grammatically incorrect. It needs additional information to convey a clear message.

5. "I don't know whom to say." - This sentence is grammatically incorrect. It should be revised to indicate whom or what you don't know to say.

6. "I don't know whom to say about." - This sentence is grammatically correct. It suggests that you are uncertain about which person or subject to mention or discuss.

To choose the appropriate expression, consider the intended meaning. If you are trying to express uncertainty about who to communicate with or mention, options 2 and 3 are suitable.