The correct answer is D.

Household penetration measures how many households bought the product, brand, category, or product group during the measured period. CMKG explains the panel-data formula as Total Number of Buying Households, or Penetration, multiplied by Spend per Buying Household equals Dollar Sales. It further explains that penetration relates to the number of households purchasing the product.

Option A describes purchase quantity or items per household, not penetration. Option B describes share of wallet or share of requirements-type spending allocation, not household penetration. Option C describes category dollar sales, not the breadth of the buyer base.

Household penetration is a reach measure. It tells whether the category is bought by many households or only by a narrow group of households.