Which of the following fluoro-compounds is most likely to behave as a Lewis base?
(1) BF₃

(2) PF₃

(3) CF₄

(4) SiF₄

Boric acid is an acid because its molecule:

Among the following, the correct order of acidity is:

1. HClO < HClO₂ < HClO₃ < HClO₄
2. HClO₂ < HClO < HClO₃ < HClO₄
3. HClO₄ < HClO₂ < HClO  < HClO₃
4. HClO₃ < HClO₄ < HClO₂ < HClO