Both say “it’s their store” it just depends whether you are talking about one or more people. Su is usually he/she but it can mean they/it if you are being non-gender specific. Personally I would go for Es sus tienda but I’m not a native Spanish speaker so I could be wrong
Answer:
16. Hablas
17. Con
18. Lo
19. De
20. O
Explanation:
Those are just my guesses and I am hispanic.
2. Ella corta las naranja.
3. Yo corto los pepinillos