Visitor Visa - B2

I am trying to get US Visitor Visa for my mother. Her application is rejected yesterday without proper reason. We need some help to understand the requirement for US Visitor Visa.

She carried all required documents to the interview as mentioned in immihelp website.

Following document are provided to VO during interview.

1. Original passport and photo

2. DS-160 Confirmation page with CEAC bar code.

3. HDFC Blue receipt

4. Interview appointment letter.

5. Form I-134 Affidavit of support form

6. Letter to Consulate

7. Invitation letter to my mother.

VO started asking questions in English though we have opted for Tamil interview

After her request, VO questioned in Tamil.

Question 1: How many children do you have?

She answered - 3 Children

Question 2: What is your husband doing?

She answered - Farmer.

Just 2 questions, VO gave 214b notice and rejected the application.

She carried all the supporting documents, but VO didn't verify them.

Supporting documents:

Employment letter

4 month Pay Stubs

Bank Letter

6 Month Bank statements

Original birth certificate

Marriage certificate

Family group photo

My Passport copy

My L1 Visa petition copy

 W2f orm and 2010 tax returns copy.

Am I missing something? I don’t really understand the reason. I am sponsoring for the VISA and all expenses. I believe VO should check only sponsor's financial status.

Any help is appreciated.

Thanks in advance!!