Select the most appropriate option to fill in the blank.

Either side of the road ______ lined by toy shops.

is

The correct option to fill in the blank is is.

The sentence is in the present simple tense, passive voice. In the present simple tense, passive voice, the verb is is or are, depending on the subject. The subject of the sentence is "Either side of the road", which is singular. Therefore, the verb must be is.

The other options are not correct because they are not in the present simple tense, passive voice.

• Has is in the present perfect tense.
• Have is in the present plural tense.
• Are is in the present plural tense, passive voice.