Which pair of events are complementary? choosing a red card from a deck of cards?

You have not provided the options, therefore, I cannot provide an exact solution.
However, I will try to help you with the concept.

Complementary events are defined as events in which only two outcomes are possible.
There is no room for a third possibility.

Examples:
1- Flipping a coin:
In this case, you either get a head or a tail. Only two outcomes are possible. These are complementary events

2- Rolling a dice to either get a 1 or a number that is not 1:
In this case, you either get a 1 or you don't. Only two outcomes are possible. These are complementary events

Hope this helps :)

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