Which of the following statements about hydrogen are correct?

1. Hydrogen has three isotopes of which protium is the most common
2. Hydrogen never acts as a cation in ionic salts
3. Hydrogen ion, H+, exists freely in solution
4. Dihydrogen does not act as a reducing agent


Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)