This puzzle took me less than five minutes to compose. With luck it will take you about the same time to solve.
cp
dt
ts
Instructions
Find two letters that, added to the above three pairs of letters, make three cross words.
You can move the above letters apart if necessary in a horizontal direction but you must not change their order or orientation.
The added pair of letters is the same in each case and stays in the same order.
What are the three words?
Please make sure that they are cross words, not just any old set of words.