Choose the option that is the passive form of the sentence.

The class teacher was taking the children to the zoo.

The children were being taken to the zoo by their class teacher.

The correct option that is the passive form of the sentence is The children were being taken to the zoo by their class teacher.

The other options are incorrect because:

• The children will go to the zoo by their class teacher is in the future tense, while the original sentence is in the past tense.
• The children can be taking to the zoo by their class teacher is grammatically incorrect. The verb "to take" is followed by a direct object, but the phrase "can be taking" is not a direct object.
• The children being taken to the zoo by their class teacher is grammatically incorrect. The verb "to be" is followed by a past participle, but the word "being" is not a past participle.