The word that is NOT an action verb in the provided options is 'happy,' as it is an adjective describing a feeling rather than an action. The other words, 'trained,' 'tested,' and 'designed' are all action verbs. Therefore, the answer is d. ;
The word that is NOT an action verb among the options is 'happy,' as it describes a state rather than an action. The other words, 'trained,' 'tested,' and 'designed,' are all action verbs. Therefore, the answer is d.
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