They ____________ wash the elephants. ✓
They have to wash the elephants.
She _____________ observe the meerkats. ✖
She doesn't have to observe the meerkats.
He _____________ help the vet. ✓
He has to help the vet.
I ______________ clean the cages. ✓
I have to clean the cages.
You ____________ feed the bears. ✖
You don't have to feed the bears.
She ______________ look after the hippos. ✖
She doesn't have to look after the hippos.