Answer :
The predicate nominative is A. lizard because a predicate nominative follows the word 'is' and can be switched with the subject (A horned toad IS a lizard, a lizard IS a horned toad)
A. Lizard
Because a predicate nominative is a word in the nominative case that completes a copulative verb [ a verb connecting a subject and a complement in the form of be].
Because a predicate nominative is a word in the nominative case that completes a copulative verb [ a verb connecting a subject and a complement in the form of be].