Answer:
Option (b) is correct.
Step-by-step explanation:
Substitute goods refers to the goods which are having positive cross price elasticity of demand. This means that there is a direct relationship between the price of one good and the quantity demanded for its substitute good.
Therefore, the threat from substitutes is high when the price of substitute is lower the price of particular good because by offering a lower price for the same product induces consumers to buy product from this seller.
The substitute goods are having the similar characterstics and provide same level of satisfaction. That's why the consumers easily switch to the product with a lower price.