Which is a pair of independent events? choosing one calendar date for sports practice and then choosing a back-up date choosing one card from a deck and then choosing one card from another deck choosing a pen to write with in class and then choosing another to let a friend use choosing a first place and then a second place work of art

The answer is 

choosing one card from a deck and then choosing one card from another deck.

These two actions are independent of each other. There is the same probability of choosing a card from any of those decks.

Let's say the decks are of 52 cards for example.

If you select one from the first deck , there are still 52 cards on the second.

Having selected from one, did not affect the other.