Which deficiency would be classified as external obsolescence?

Explanation:

External obsolescence is an type of depreciation; a defect, usually incurable, caused by negative influences outside a site and generally incurable on the part of the owner, landlord, or tenant. Also known as a loss of value from all causes outside the property itself.

When a residential building is situated in a commercial environment 

Residential and commercial buildings dont tend mix well in suburban areas. It’s usually a negative factor when houses are located next to restaurants, retail, gas stations, offices. You could classify this as a deficiency

D.

Explanation:

If good A and good B are substitutes, then the demand curves for both goods are correlated. If the price of good A increases, then consumers will prefer good B and the demand curve for good B will increase and shift to the right. This happens because consumer can replace easily good A for good B and vice versa. And because of this, consumers are sensible to price changes of the two goods.

In this case, the price of bagels decreased and because consumers can replace easily bagel for doughnuts, they will prefer the cheaper good: bagels. If a large portion of consumers stop buying doughnuts because now they replace them for bagels, the demand curve for doughnuts will decrease and shift to the left.