Answer:
2) Before you eat the sandwich, please cut it in half.
4) When we are ready to leave, we will send you a text message.
5) If she starts to get warm, Janna will turn on the air conditioner.
Step-by-step explanation:
A complex sentence is that sentence which has one or more independent clauses and is separated by a comma or conjunction.
Therefore, the examples of complex sentences from the given options are option 2, 4 and 5.