4. The writer says that to use animals, zoos and animal shows must now

Решение:

В тексте говорится: "These days, zoos are still for entertainment, but they also try to protect animals and teach people as well. In addition, both zoos and animal shows must follow rules." Это означает, что сейчас зоопарки и шоу должны соблюдать правила.

Ответ: c. follow certain rules.