“Have to” is used to express certainty, necessity, and obligation.
1.I have to finish this report before our conference call with the client.
2.This has to be right, I read the instructions ten times.
3.The polenta has to be stirred continuously otherwise it will stick to the pot.
4.She has to leave early today.
5.My niece has to read four books this year for her literature class.
6.I have to print all of our hotel confirmations before we leave for the US.
7.You don’t have to tip the waiters but if you do they will be very grateful.
8.The receptionist didn’t have to be so rude to us.
9.My friend had to fire six people last week because they were stealing from the company.
10.When you travel often, you have to be very patient because it can be stressful.