The correct form of the verb 'tener' for the subject pronoun 'ustedes' is '¿Tienen leche?'
The appropriate form of the verb "tener" for the subject pronoun "ustedes" is ¿Tienen leche?
In Spanish, 'ustedes' is the unisex formal plural form, which requires the verb 'tener' to be conjugated as 'tienen'.
Remember that verb conjugation in Spanish varies based on the subject pronoun used, so it's essential to match the verb form with the correct pronoun.