Four cards lie on a table. Each card has a number printed on one side and a colour on the other. The faces visible on the cards are $2,\;3,\;red,\;and\;blue$.
Proposition: If a card has an even value on one side. then its opposite face is red.
The cards which MUST be turned over to verify the above proposition are
- $\text{2, red}$
- $\text{2, 3, red}$
- $\text{2, blue}$
- $\text{2, red, blue}$