The correct answer is A. 0.4.
The support percentage is the percentage of transactions in the database that contain the specified items. In this case, the items are milk, bread, and cheese. The support percentage for the association rule “if milk and bread are purchased, then cheese is also purchased” is the percentage of transactions in the database that contain both milk and bread, and also contain cheese.
To calculate the support percentage, we first need to calculate the number of transactions that contain milk and bread. This is 4, since 4 of the 5 transactions in the database contain milk and bread. We then need to calculate the number of transactions that contain milk, bread, and cheese. This is 2, since 2 of the 5 transactions in the database contain all three items. The support percentage is then 2/5 = 0.4.
Option B is incorrect because it is the confidence percentage, not the support percentage. The confidence percentage is the percentage of transactions that contain the specified items in the consequent (cheese) that also contain the items in the antecedent (milk and bread). In this case, the confidence percentage is 2/4 = 0.5.
Option C is incorrect because it is the lift percentage, not the support percentage. The lift percentage is the ratio of the confidence percentage to the support percentage. In this case, the lift percentage is 0.5/0.4 = 1.25.
Option D is incorrect because it is the coverage percentage, not the support percentage. The coverage percentage is the percentage of transactions in the database that contain at least one of the specified items. In this case, the coverage percentage is 4/5 = 0.8.