Quote
my son has refused to write since he was in kindergarden.
This may be a red flag. Has he been evaluated for dysgraphia? There are many sources of information available, to learn about dysgraphia. Here is one page of resources from the Davidson Database.

Quote
He may think that I am not qualify to answer his questions.
Parents do not need to be qualified to answer our kids' questions, the next generation can learn more than what the parents have learned. Some may say the next generation NEEDS to learn more.

Quote
He was asking these question after he figured out the answers " and I dont know what does his motive.
Kids may test their parents to see what they know. There was a game show on TV a few years ago called "Are you smarter than a 5th grader?" While it is an attention-getting title, even when the 5th grader outscored the adult, it was largely due to the test questions being items recently learned by the 5th grader and not readily recalled by the adult as they may not tend to be bits of knowledge utilized frequently; The adult has acquired much more knowledge in areas which were not quizzed on the TV show. It is often the same for parents: Children may revel in their new-found knowledge with each fact they learn and wish to know if their parents also have that knowledge.

Quote
I know I have to learn to stop him to be rude to me at some point.
Immediately. Hopefully your husband will be glad to help with this. A person's character and resultant quality of interpersonal relationships may ultimately take them farther in life than their IQ or accumulated knowledge.

While this may vary by family, some may say that simply observing that you do not know something, or noting than he has more interest or depth of knowledge in a topic than you may not be rudeness.

However, treating you (or any other person) as though the person has worth only when they can be of assistance is rude.

What does your son say or do to be rude? For example, does he:
- Use a negative, condescending, or pejorative tone of voice?
- Use demeaning body language, such as: roll his eyes, shake his head, smirk?
- Ignore you, such as: refuse to look at you, withhold a response when you speak to him?

Addressing specific behaviors may be a good starting point. Ongoing discussion of appropriate/acceptable responses and interactions may be of help. Children learning to demonstrate respect for parents, teachers, adults, and peers even when one may know more in a particular area than the parent/teacher/adult/peer is important.