Which of the following sentences uses homophones incorrectly?

Mom told me that she needs me to knead the dough every hour.
The Secret Service thought it would be best to have a plain plane.
The student erased her whole paper and made a large hole.
The principle of the school makes decisions based on his principals.

Question

Which of the following sentences uses homophones incorrectly?

 Mom told me that she needs me to knead the dough every hour.
 The Secret Service thought it would be best to have a plain plane.
 The student erased her whole paper and made a large hole.
 The principle of the school makes decisions based on his principals.

ltrout · Answer

They all look correct to me? O.o

twistrose · Answer

The last one.