how to get the answer of 3 radio buttons and msg.box ( you got correct answer) or ( wrong answer)

There are many possible ways of implementation you could use here, and OriginalGriff has given you excellent suggestions.

A key question is: what is your goal here ? To create a one-off solution where all the logic and events happen in one Windows Form ? Or, to create a general solution that you can re-use in other projects, and to which you can add new features (extensibility) ?

Specific suggestions, whether your goal is one-off, or re-usable: don't use a separate Form for each question:

1. use a single Panel, or other ContainerControl, to hold the RadioButtons and other Controls you need, and re-use those Controls, changing their content for each question.

2. if you had additional content unique to each question (a picture ?), you could consider using a TabControl, with unique content for each question on each TabPage.

3. fyi: an alternative to checking one RadioButton at random is to set the Checked value of all RadioButtons to 'false at the start of each question. this may avoid a slight unconscious bias of the person taking the test to consider the checked value as being, possibly, more likely to be correct.

4. if your goal is a re-usable solution, consider using classes, to "model" both the collection of Questions/Answers, and individual Question/Answers. ask for help here with that, if you wish.

Hello,
When user selects the answer and hits next button check for correct answer, if it is correct add a count to session and open next form, in next forms increment count if answer is correct.

1)instead of 5 forms you can change the text of the radiobutton and maintain a flag which question is to be shown.

2)to check how many correct answer declare 2 public variable and assign value on checked change of radio button.