A Local Consumer Reporter Wants to Compare the Average Costs

A local consumer reporter wants to compare the average costs of grocery items purchased at three different supermarkets, A, B, and C. Prices (in dollars) were recorded for a sample of 60 randomly selected grocery items at each of the three supermarkets. In order to reduce item-to-item variation,
The prices were recorded for each item on the same day at each supermarket.
$\begin{array} { c l r c c } \hline & { \text { Item } } & \text { A } & \text { B } & \text { C } \\\hline \text { 1) } & \text { paper towels } & 1.23 & 1.43 & 1.38 \\\text { 2) } & \text { cereal } & 2.70 & 3.15 & 2.90 \\\text { 3) } & \text { floor cleaner } & 6.09 & 5.97 & 6.98 \\\vert &\vert&\vert&\vert& \vert \\59 ) & \text { shaving cream } & 1.09 & 0.99 & 1.05 \\60 ) & \text { canned green beans } & 0.55 & 0.70 & 0.47 \\\hline\end{array}$


Identify the blocks for this experiment.

A) the 60 grocery items
B) the $60 \times 3 = 180$ prices
C) the three supermarkets
D) the day on which the data were collected