The addition of HBr to 1-butene gives a mixture of products A, B and C.

The mixture consists of

1. A and B as major and C as minor products

2. B as major, A and C as minor products

3. B as minor, A and C as major products

4. A and B as minor and C as major products

Hint: Markownikoff's rule
 
The alkene is unsymmetrical, hence will follow Markownikoff's rule to give major product. The major product is 2- bromobutane and minor product is 1-bromobutane. The 2-bromobutane contains a chiral center hence racemic mixture is obtained. So, products A and B are major and product C is minor. The reaction is as follows: