Which of the following statements about hydrogen is/are correct ?

1. Hydrogen has three isotopes of which protium is the most common
2. Hydrogen ion( H positive ion) exits freely in solution.
3. Dihydrogen, H2 , acts as a reducing agent .

select the correct answer using the code given below?

1. 1, 2 and 3
2. 1 only
3. 1 and 3 only
4. 3 only