Show that each of these conditional statements is a tautology by using truth tables.

a) (p ∧ q) → p
b) p → (p ∨ q)
c) ¬p → (p → q)
d) (p ∧ q) → (p → q)
e) ¬(p → q) → p f ) ¬(p → q) → ¬q