Answer: Shortage; Rise
Step-by-step explanation:
I suspect that there are options to this question but the correct options should be along the lines of the above.
The price in lettuce doubling with all else being equal is due to the drought that has reduced the supply of lettuce. The Law of Supply and Demand posits that when Supply drops, prices rise. The prices of Lettuce rising is therefore due to a SHORTAGE of Lettuce.
Seeing as a chief ingredient of Tacos being Lettuce has seen it's price rise, acquiring it to make Tacos will be more expensive and this will need to be reflected in the cost of the Tacos which means that the price of Tacos will RISE.