Question

8.2 write questions: is this / that your...? or are these / those your...?
68.3 complete the sentences. use this / that / those / those + these words:
birds house plates postcards seat shoes

Explanation:

Sub - question 4

Step1: Analyze the noun and quantity

The noun here is "postcards", and it is a plural noun. For plural nouns that are relatively far (in the context of the picture, the postcards are on a rack, a bit away from the speaker), we use "those".
So the sentence should be "How much are those postcards?"

Step2: Form the complete sentence

Putting it together, we get "those postcards" to fill in the blank.

Step1: Analyze the noun and quantity

The noun here is "seat", and it is a singular noun. The seat is relatively close (in the context of the picture, the seat is near the woman at the table), so we use "this".
So the sentence should be "Excuse me, is this seat free?"

Step2: Form the complete sentence

Putting it together, we get "this seat" to fill in the blank.

Step1: Analyze the noun and quantity

The noun here is "plates", and it is a plural noun. The plates are being held by the chef, and in the context, they are plural and we use "these" (since they are relatively close to the speaker, the chef).
So the sentence should be "These plates are dirty."

Step2: Form the complete sentence

Putting it together, we get "These plates" to fill in the blank.

Answer:

those postcards

Sub - question 5