2. Yes. It's hard to express. Use enumeration. Or directly {all prime numbers}

3. The relationship is established.

4. It doesn't belong to. Empty set is nothing, 0 is still a thing.

5. Yes, it doesn't matter if you change your position.

6.{ All existing municipalities in China | Beijing, Tianjin, Shanghai and Chongqing}

7. I don't know what this means ... not necessarily. The setting can be "a boy with a hat and glasses", so it has three characteristics.

8. Yes. Generally, you have to write. It doesn't matter if you don't write, but you may be deducted.

9. Not bad.

10.( 1)A={ a prime number greater than 1 and less than 100}

(2)B={ parallelogram}

11.a = {x = 2k+1k ∈ n * and x < 1000}

12. A positive divisor is a positive integer divisible by a given integer.

Prime factor: every composite number can be written as the product of several prime numbers, which are called prime factors of this composite number. If a prime number is a factor of a certain number, then it is said that this prime number is a prime factor of this number.

13.A={ trapezoid}

B={ rectangle}

And so on ~

I'd better add some. I feel so tired.