#3. “When the room is clear, let’s get organized and plan the meeting.”
This is because the vocabulary used is very simple and the “let’s” gives us an indication of informality and familiarness.
The other sentences use strong verbs such as “create,” “establish,” and “develop” and they use creative/formal nouns like “agenda,” and “protocol, and “strategy.”
Hope that helped. Sometimes you can just sound out the sentence and it pops right out to you - it takes some practice, tho.