Choice "D" is correct. If an item has many similar substitutes, its price elasticity of demand will be high. Customers can always switch to a substitute, so a change in price may affect demand substantially.
Choice "a" is incorrect. If the cost of an item is low compared to the total budget of the purchasers, it will make little difference how much it costs. For example, in a business the cost of paper clips will probably not be a significant factor.
Choice "b" is incorrect. If an item is considered a necessity (e.g., insulin to diabetics), the price elasticity of demand will be relatively low (i.e., inelastic). Purchasers will buy it regardless of the cost, and demand will not change all that much.
Choice "c" is incorrect. If the price of an item is regulated by a government agency, the demand may not be highly price elastic because any price changes (if made) will be controlled and implemented gradually over time.