Select the correct passive form of the given sentence.

We mow the lawn once every month.

The lawn is mowed once every month.

The correct passive form of the given sentence "We mow the lawn once every month" is The lawn is mowed once every month.

The other options are incorrect because:

• The lawn was mowed once every month uses the simple past tense, while the original sentence is in the present tense.
• The lawn has been mowed once every month uses the present perfect tense, which is not typically used for actions that happen regularly.
• The lawn will be mowed once every month uses the future tense, while the original sentence is in the present tense.