What is the nature of reaction when sulphuric acid is dilutes with water ?

The acid formed when sulphur trioxide reacts with water is

When a substance A reacts with water it produces a conbustible gas B and a solution of substance C in water. When another substance D reacts with this soution of C , it also produces the same gas B on warming but D can produce B on reaction with dilute sulphuric acid at room temperature. B on reaction with dilute sulphuric acid at room tempreture. A imparts a golden yellow colour to a smokeless flame of bunsen flame. A,B,C and D are respectively.

The reaction between zinc and dilute sulphuric acid is a

You are provided with 90 mL of distilled water and 10 mL of concentrated sulphuric acid to prepare dilute sulphuric acid. What is the correct way of preparing dilute sulphuric acid? Give reason.