Correct sentence:
Some meerkats are busy finding food, while others stand on their hind legs to keep watch.
Why this is better (easy words):
- "Stand on their hind legs" is a clearer way to say "stand on two feet." Meerkats usually stand on their back legs.
- "To keep watch" (or "to watch for danger") is clearer than "to watch out." "Watch out" is something you say to warn someone.
- The comma before "while" helps the sentence flow because it shows two different things happening at the same time.
Other simple ways to say it:
- Some meerkats look for food while others stand up to watch for danger.
- Some meerkats are finding food; others stand on their hind legs and watch.