The correct answer is D. No Error.
The sentence is grammatically correct. The subject and verb agree in number, and the object of the preposition "from" is correctly plural.
Option A is incorrect because the subject and verb do not agree in number. The subject is "Mr. Alexander," which is singular, but the verb is "has purchased," which is plural.
Option B is incorrect because the word "furnitures" is plural. The object of the preposition "from" should be singular, because it refers to a single purchase.
Option C is incorrect because the word "new" is not necessary. The sentence is already clear that the furniture is new, because it is being purchased from a store.