The word "approve" is used to refer to when someone agrees with other's opinions or ideas. It is an expression of favoring something.
<u>The word "approve" is a verb and has been used in the given sentence to show that the principal confirmed with the idea or request of Mr. Juarez of taking the students to the beach for two days study of whales.</u>
The word "approve" has been used to refer that the principal has sanctioned officially the request of Mr. Juarez.
So, the correct answer is 'give official permission.'
