Answer:
calcium chloride and silver nitrate
Step-by-step explanation:
A precipitate is often formed in a double replacement reaction when the reaction yields an insoluble product.
Consider the reaction between calcium chloride and silver nitrate;
CaCl2(aq) + 2AgNO3(aq) -------->2AgCl(s) + Ca(NO3)2(aq)
AgCl is insoluble in water, hence the reaction leads to the formation of a precipitate.